AudioCircle
Other Stuff => Archived Circles => Hypex Owners Circle => Topic started by: serengetiplains on 24 Jun 2012, 07:42 pm
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I notice the Ncore tweak thread is locked. Is this topic verboten?
Here are a few avenues for improvement I can see from a distance:
1. Operate Ncores in bridge mode.
2. Preregulate the input and driver supply rails---for instance with Hynes regs. Ideally I'd put a Hynes shunt reg as the last regulator before the circuit it's powering.
3. Bypass psu electrolytic and output filter capacitors with styrenes or teflons---for instance with these:
http://www.ecicaps.com/capacitors/features/mt1-series-teflon-polytetrafluoroethylene
4. Replace critical resistors (feedback, etc.) with Vishay smds.
5. Bi-wire multi-driver speakers.
6. Shield the psu from the Ncore module.
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I suggest you purchase the modules and do to them as you suggest then report back with results. Objective and subjective results of course.
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I will be so doing, JT. I've performed most of these mods on Tact amplifiers to surprisingly good effect. I'll report back with my findings for the Ncores here.
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I'll report back with my findings for the Ncores here.
:o
Great! :thumb:
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I'm assuming that you will first only modify one channel (or one monoblock) so that you can make more valid comparisons to the unmodified one?
Steve
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Steve, I'll begin with unbridged Ncore modules driven by a SMPS600, then will add a second Ncore to each channel, then will add some Hynes regs, then resistors, capacitors, etc., in some such stepped progress. PSU to Ncore wiring will be kept as short as possible (max 2" if I can swing it), with Ncores and PSUs mounted on either side of an aluminum plate.
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One thing, just don't mention anything here about tweaking the fuses. Everyone here gets upset.
Mama don't allow no tweaking the fuses. :nono:
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Mum's the word on those pesky fuses, I promise. :shh:
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One thing, just don't mention anything here about tweaking the fuses. Everyone here gets upset.
Mama don't allow no tweaking the fuses. :nono:
They don't mind if you do it right. Unsolder the fuseholder from the PC board and replace it with a rhodium over gold plated pure beryllium copper fuseholder. It wouldn't make much sense to just pop an audiophile fuse into a standard cheap nickel plated tin fuseholder.
Steve
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It wouldn't make much sense to just pop an audiophile fuse into a standard cheap nickel plated tin fuseholder.
Indeed.
One could then explore replacing the copper traces to and fro the gold plated pure beryllium copper fuseholder with, say, carbon nanotube bybee-sandwiched cryod-n-levitated superleads. Kinda gets my heart rate up just mentioning it.
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I'm thinking powering the input module from a 12V tranny with say a 10.000uF/20V jensen 4-pole (and rect. ofc).
Btw AMR 5A fuses blow at poweron :roll:
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Btw AMR 5A fuses blow at poweron :roll:
I believe the fuse should be a 5AT- five amp time delay or slow blow.
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Hey All,
I don't own the Ncore amps yet, but I saw this over on Audiogon:
http://app.audiogon.com/listings/core-audio-technology-hypex-ncore-linear-power-supply
6K and pure Ncore bliss....
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Hey All,
I don't own the Ncore amps yet, but I saw this over on Audiogon:
http://app.audiogon.com/listings/core-audio-technology-hypex-ncore-linear-power-supply
6K and pure Ncore bliss....
I'm not personally seeing anything like $6k USD in the images. $2k might be worth considering, $3k getting up there, $4k too much...jumping to $6k seems way out there. No faceplate image? My 2c.
Me hopes their product value and performance exceed their website editing: Even paired with their stock Switchmode power supply they provide one of the very best sonic experiences amplification has to offer.
Emphasis added. I'm reminded of Winston Churchill's reply when accused of using too many prepositional phrases: "This is petulance, up with which, I shall not put."
(Unrelated...his reply to a woman who accused him of being drunk: "I may be drunk, but in the morning I shall be sober. Conversely, you shall still be homely.")
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Do you realize that you are getting two of the chassis you see.....one for each channel? That's a lot of expensive Mundorf caps, etc. I think 6K is fine for all that. You even have Mundorf silver/gold/oil caps in the AC filter that is not shown...this is some serious tweak here.
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I'm not personally seeing anything like $6k USD in the images.
$6K is for the power supplies and chassis, you do still have to add your own NC400 modules.
Steve
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Do you realize that you are getting two of the chassis you see
No. Please re-read my criticism. "in the images", not the text and images. I can't read text as stupid as what I quoted so I stopped. The image + price quoted = bad value, and you seem to agree.
Seriously, maybe you should drop him a note to include two in his image.
.....one for each channel? That's a lot of expensive Mundorf caps, etc. I think 6K is fine for all that. You even have Mundorf silver/gold/oil caps in the AC filter that is not shown...this is some serious tweak here.
Serious is worse than vague, sorry. What's your estimate for the parts cost for two? T'would be so much more "serious" to read independent feedback, direct A-B vs. SMPS600, no?
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$6K is for the power supplies and chassis, you do still have to add your own NC400 modules.
Steve
Yes, I noticed that, thanks.
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Me hopes their product value and performance exceed their website editing:
There's nothing wrong with the grammar - "amplification" is the subject of an adjective clause modifying "experiences," and it need not agree in number - if that's the issue to which you're referring, as Mr. Churchill might feel compelled to say.
And on that last point, it should be noted, Churchill was referring not to the problem of too many prepositional phrases, but to the proscription by too many tight-sphinctered grammarians against the practice of ending a sentence with a preposition.
"Me hopes," on the other hand, wouldn't pass muster with most 21st Century copy editors. :lol:
More importantly, I can testify that these power supplies are mighty effective - and yes, looks like you get two of 'em! 8)
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I'm not personally seeing anything like $6k USD in the images. $2k might be worth considering, $3k getting up there, $4k too much...jumping to $6k seems way out there. No faceplate image? My 2c.
Me hopes their product value and performance exceed their website editing:
Emphasis added. I'm reminded of Winston Churchill's reply when accused of using too many prepositional phrases: "This is petulance, up with which, I shall not put."
(Unrelated...his reply to a woman who accused him of being drunk: "I may be drunk, but in the morning I shall be sober. Conversely, you shall still be homely.")
I am more tickled by the $6000 LIQUID music server that weighs 150 pounds. Maybe he will include a couple of freshwater Piranhas in that fish tank...:icon_twisted:...but alas they will not survive in mineral oil. Good to clean earwax though.
:duh:
Anand.
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Thanks for the tip, Rodge.
Guys, what's the need to ridicule? If those supplies lack the value you claim they lack, who would then care to even talk about them? Next ...
My tentative priority for Ncore power supplies is starting to shape up like this: comparator supply is most important, followed closely by the driver supply, followed by the input buffer supply. My sense is that the output supply is less important for overall sonics than any of those three, although important in its own right.
Regarding the output rails, electrolytics, to me, sound like mud in the audio band, so I'll experiment with bypassing electrolytics on the output rails, claims of parasitic resonance notwithstanding (a few big and a few tiny teflons on my Tacts, carefully placed, and wow the mud reduction). Also, the lower the noise the better, clearly. But I question if a regulated supply could be feasibly designed to supply current quickly enough (a maximum 27 amps of which) and be able to sink energy. If one doesn't regulate, the best solution is differentially cancel noise via rails carrying mirror noise voltages. Bruno says his smps's synchronous secondary rectification gives this for that use within the Ncore's differential circuitry. I'd have to see a schematic to see how he puts this to effect, but it makes implicit, well-thought sense. Perhaps a linear supply will better the Hypex switcher. There are a few reasons to think this might not obviously be the case.
Bridging should also noticeably reduce output-supply-related noise.
I don't know if the comparator can be independently supplied without mucking something up. If it can be, I'll be tempted to put a Hynes shunt on it, fed by a Hynes series. The driver supply can be regulated easily (and which I think would function as preregulation). Same for the buffer supplies.
These amps might really, really fly.
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I am more tickled by the $6000 LIQUID music server that weighs 150 pounds. Maybe he will include a couple of freshwater Piranhas in that fish tank...:icon_twisted:...but alas they will not survive in mineral oil. Good to clean earwax though.
:duh:
Anand.
Yeah, pretty far-out, I gotta say... that's one amp you don't want to knock off the shelf! :lol:
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I wish Bruno had consulted with more forum members before designing and selling me his crummy SMPS600!
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Btw, my Tact is a Lyngdorf Millenium. I replaced the digital main supply and all regulators (5) each with tx-->Hynes series-->Hynes shunt. All the electrolytics are well bypassed, output filter caps likewise. Higher frequencies are slightly elevated (probably the caps), but in all other respects, this amp sings. Crystal-clear see-through and class D tone glory --- the better of what class D does well, better (notwithstanding lacking the deep coherence and timbre of class A push-pull SE, err).
The Ncores will be an interesting competition. Digital vs. analogue class D.
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And if the comparator is differential (can comparators be differential?), then one supply for the both. Differential supply distortion.
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serengetiplains, any views on the minimum amount of capacitance needed for the buffer section? Im contemplating skipping electrolytics alltogether and bundle cheap russian caps.
edit:
Positive DC voltage on J1:3 output - 21 - Vdc See note 1,2
Negative DC voltage on J1:7 output - -21 - Vdc See note 1,2
Looks like its a balanced supply with a ~42 volts potential. Didnt notice this before (didnt look very closely). So you'd need 2 lineair supplies and optionally 2 Hynes regs, this wont be an ultra cheap upgrade 8)
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For only $2700, you can add the Stillpoint footers and Stillpoint standoff mod.
Core Audio, now where have I seen that name before?
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And the plot thickens:
http://www.diyaudio.com/forums/vendors-bazaar/190434-hypex-ncore-461.html#post3074569
http://www.whatsbestforum.com/showthread.php?3618-Class-D&s=7faebcfdf0fa2e6c4a2082f8933b5324&p=118349&viewfull=1#post118349
I find it interesting that Gary's words were copied verbatim onto the Audiogon ad:
http://www.whatsbestforum.com/showthread.php?3618-Class-D&p=118354&viewfull=1#post118354
:rotflmao:
Anand.
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serengetiplains, any views on the minimum amount of capacitance needed for the buffer section? Im contemplating skipping electrolytics alltogether and bundle cheap russian caps.
edit:
Positive DC voltage on J1:3 output - 21 - Vdc See note 1,2
Negative DC voltage on J1:7 output - -21 - Vdc See note 1,2
Looks like its a balanced supply with a ~42 volts potential. Didnt notice this before (didnt look very closely). So you'd need 2 lineair supplies and optionally 2 Hynes regs, this wont be an ultra cheap upgrade 8)
It is a differential supply. Bruno has placed what he calls the equivalent of an HxR regulator on-board the Ncore supplying the buffers. The Ncore data sheet specifies that the minimum voltage input to those supplies is 16V. I suspect the HxR-equivalent regulates to 12V, so with a, say, 3V dropout you need 15V, hence the 16V minimum (the extra V allowing for line-level fluctuations). The DCV of the smps buffer supplies is nominally 21V, so a Hynes reg of, say, 17VDC rating with DC input from the smps will work just fine in this context. That upgrade will not be too expensive.
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My trouble is the qualifier "improvement". If I add decals to my amp, is it "improved?" Maybe yes to certain individuals.
Personally, I'd rather past, present and future similar threads be banned containing untested qualifiers like "improved". I'd accept in their place the following:
Independent blind ABX listening test with at least a dozen independent audiophiles with no financial interest whatsoever with 100% consistently preferring the "modded" amp. IMO the $6k cost of the linear PS justifies my 100% requirement. DIY and lower cost mods could qualify with lower approval percentage. Personally, it will be a cold day in hell before I modify my amp so that Hypex refuse to service it, which describes many if not most of the described "improvements." That is not an improvement. That is stupidly converting a perfectly fine amp in to an unserviceable toy, something I've owned and have no interest in. Just my opinion.
Or alternately:
Send the modded amp out to OEM-stock properly-built NC400 owners and post their reaction, something like maybe -5 to +5 rating scale:
-5 much worse than OEM
0 no difference
+5 much better than OEM
If the mod is indeed thus determined "improved" above, then indeed the word "improved" makes sense. Otherwise it's pure conjecture and absolutely nothing else.
IMO my position is easier to justify than labeling Ncore "improved" with absolutely no justification except, "This always improved prior amps!" And that's all I've read to now, and I've read (I think) every "improved" post at AC. That's my story and I'm sticking to it! :lol: It's perfectly fine to disagree. I don't require any justification to disagree. Toss this post in the garbage if you like. It's just my preferred position.
I bought the Ncore sight unseen and sound unheard based on independent user reports, and because my need for better amps was urgent. I based none of my purchase decision on financially biased opinions. Conversely, in fact, I based my decision on the opinions of some persons who might be stuck selling their current amps, and whose opinions might negatively impact resale value! That carries absolutely immense weight IMO!
Lastly, the $6k linear PS sellers mention the quality of the NC1200 and AFAIK no one's heard it except OEM buyers and some select reviewers. Pretty far fetched of a guy taking images on his carpet posting comments about the NC1200, sorry. Oh, and he implies an OEM Hypex PS exists for the NC1200 and this is a false claim. There are some untested methods to allegedly obtain US patent a small fraction of the normal cost of about $15k USD ($10k to file the patent, about $5k to contest legal claim...virtually every patent claim is contested by individuals who's purpose is to contest every patent claim...it is a war of attrition and they don't stop until they've tested the claimant's financial will and ability to the tune of about $5k). Again, somehow I presume someone taking images on his home carpet has absolutely no funds to justify his comments concerning patent protection. Patent requires complete and absolute scientific disclosure of the circuit, which many of the readers of this thread would immediately copy for DIY purposes, plus the design would be instantly common knowledge.
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James, you're sounding very defensive, preemptive defensive, in fact. I don't care that you don't care, and if in fact you don't care, play somewhere else. Seems to me you care. Which is it? I don't need your approval to run my audio preferences.
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I reply to the so far unjustified (to me) claim of "improved." That's it. A better term is "modified." I think, even by your own standards, it has to "compared" to be labeled "improved" does it not?
Amplifier A does not equal amplifier B. In this case, A = stock OEM properly built/properly functioning NC400/SMPS600, B = A + "modifications". A and B are never directly "compared" in any way.
Please list and describe now the conditions in which B can be properly described as "improved" vs. A.
IOW, how can B be "improved" vs. A when the two are never directly compared?
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Let me give you an English lesson. The word "improvement" in the thread title implies "potential improvement." Nothing more. Actual improvements, if any at all, will be reported---at the earliest *after* I receive an actual Ncore module.
But back to my question, which I'll restate. If you think the Ncores cannot be improved, why are you wasting your (and our) time here?
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Gentlemen,
PLEASE stop the back and fourth and be kind. :)
http://www.audiocircle.com/index.php?topic=37305.0
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For the record, I'd be happy to hear a modified Ncore to see if it was improved. Sorry for any apparent bad feelings about this, which was and is not my intent. I also have interest in reading about the mods too btw.
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For the record, I'd be happy to hear a modified Ncore to see if it was improved.
I have interest in objective data on an "improved" NCore.
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serengetiplains, Do you know if Paul Hynes makes any surface mount replacement regulators. I don't see any through hole devices on the Ncore modules board.
Scotty
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Scotty, I believe Paul does not. He does make smallish series and shunt regulators measuring 1" x 1.5" thereabouts, but these are through-hole. With a careful soldering hand, and a little luck with circuit traces, these can be placed right near the chip they're powering. Their small form-factor is beneficial as circuit traces are short, benefiting performance. Pricing is in the range of £30 to £36 thereabouts, or was when I last purchased some.
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If that is the case then I foresee some potential problems getting them in place due to the parts density on the module. I do know that regulation at radio frequencies which is what we are essentially dealing with here is a point of use proposition. Lead inductance or circuit board trace inductance will kill you at these frequencies.
Scotty
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I do know that regulation at radio frequencies which is what we are essentially dealing with here is a point of use proposition. Lead inductance or circuit board trace inductance will kill you at these frequencies.
I understand that, Scotty. I do not yet know how the comparator is powered, but I speculate that placing a Hynes reg near the chip(s), if that is feasible given the circuit board layout, will put the regulated supply nearer the chip than the stock supply.
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Interesting discussion :) One of the masters of quiet circuits is John Curl. I have read his comments on regulators. He seems to like
power supply circuits with several levels of regulation. If one buys into the idea that the power supply is in the signal path ( Stan Warren ) then I think it is wise to at least experiment with them as a possible avenue of improvement.
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That's my pov likewise, Mike. I go for double-regulation supplies for all critical components, where I feed a shunt reg with a series reg, and feed the latter with its own dedicated transformer to prevent ground current mixing. Paul's shunt regs are a bit noisier than his series models, but from my and others' experience of these, his shunts are the better performers for digital supplies. They work best if fed from a very quiet (hence series) supply. The tx-->series-->shunt topology is very quiet, particularly with AC conditioning on the front end.
Btw, here are basic specs for his shunts:
slew rate 5,000 volts per microsecond
gain bandwidth product 1 GHz
rise time < 1 nanosecond
settling time < 10 nanoseconds
wideband noise 2 nanovolts root HZ
output impedance is less than 0.001 ohm
power supply line rejection ratio is 110 dB from DC to 200 KHz
Compare these specs to HxR specs.
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Here are HxR specs:
(http://www.audiocircle.com/image.php?id=64413)
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I don't know enough to say how it should be done but I do know this from years of sold engineering.
Implementation is key. Swapping parts will not always and usually doesn't yield a better result. It can simply give you a differerent result which often times is taken as better.
EDIT: and this is why objective data is SO important.
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I understand that, JT. Implementation is key and implementation is not all---what is implemented also counts (well implemented junk = junk, or some variation thereof).
I replaced some smd regs---you know, the 317 textbook-variety that engineers are so fond of---on my Lyngdorf. The Hynes regs that replaced these were powered by series regs placed some 6" to 8" away, powered by dedicated transformers another 10" away or so. The shunts added a small amount of overall length to the supply leads.
Let's add up the pros and cons:
PROs
1. vastly better *shunt* end-regulator
2. fed by a vastly better preregulator
3. which for its part is 6-14" closer to the shunt and
4. powered by a dedicated r-core transformer which is
5. less affected by amp-related line disturbances and
6. galvanically isolates the series-shunt combo to eliminate ground current voltage variations
CON
1. one cm added lead length (note: the 317s the shunts replaced are 2" to 8" distant from the chips they power, so I'm unconcerned about adding an extra cm)
There's some objective data for ya. Listening confirmed this objective data, so I was objectively happy.
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There's some objective data for ya. Listening confirmed this objective data, so I was objectively happy.
I prefer the objective measurement data. :wink:
Kind of like this:
http://www.audiocircle.com/index.php?topic=107040.msg1097394#msg1097394
That unit is $10k for the base. The AP that Hypex (Bruno says they have 4) and many other audio company's use are $40k+. That's what it takes though....
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Before mods can be undertaken someone will have to dismount the board from the "heatsink" and analyze the circuitry. The board is at least a 2 layer board and possibly more and it has been designed to be resistant to cloning which may additionally complicate matters.
It may be awhile before we see any list of recommended mods due to the aforementioned complications.
Scotty
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Yeah, skeptical. After reading the details of how the smps600/nc400 combo work in unison, and given the extreme performance numbers, you are going to have to better those numbers, rather than say "a veil was lifted" after I installed these parts.
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Yeah, skeptical. After reading the details of how the smps600/nc400 combo work in unison, and given the extreme performance numbers, you are going to have to better those numbers, rather than say "a veil was lifted" after I installed these parts.
WOW. I'll actually agree wtih you here.
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I think it's a four-layer board, Scotty, so it's worse than you first said.
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Kind of like this:
http://www.audiocircle.com/index.php?topic=107040.msg1097394#msg1097394
Here's Bruno. I'll leave you to gauge the relevance of his comment to what I'm wanting to accomplish by reducing power supply noise (= effectively increasing PSRR).
An FFT of a sine wave says nothing about frequency response, THD at other frequencies or output impedance. Also, it says little about the PSU. An amplifier with bad PSRR on a regulated supply and an amplifier with good PSRR on an unregulated supply post equally clean FFTs.
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Speaking of FFTs Mike did one on his Ncore and it looked pretty good.
(http://www.audiocircle.com/image.php?id=63435)
Link to thread here http://www.audiocircle.com/index.php?topic=107040.0
Scotty
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That unit is $10k for the base. The AP that Hypex (Bruno says they have 4) and many other audio company's use are $40k+. That's what it takes though....
I want to comment on this. I'm just a joe who likes music. I have no access to expensive testing gear, as very few do, and I lack both technical and training knowhow to operate such. Do you really expect that someone like me will have proper testing gear? If you don't, why do you keep asking me (the guy now typing who like most others interested in good music replay has no access to this gear) for objective data that only this gear can provide? Do you want to relate to me, or are you commenting to some fictional person to make a point that cannot be answered?
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I think the point is that unless you can back up the changes as "improvements" with concrete gains in measured performance, all you can do is provide your biased self-assessments of the effects, which may in fact be merely differences you prefer, rather than objective performance gains. As a result, while you may prefer the modifications, there is nothing to suggest that anyone else will....
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EDIT: and this is why objective data is SO important.
I agree.
What objective data(test measurements, specs,etc,...) did you use when you
were comparing the TRL Dude to other preamps?
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Having been in the hobby for more than 35 years, it has been my experience that while we can measure many performance parameters we cannot measure how an amplifier or a circuit will be perceived to "sound" by a human being.
It is probably possible to improve on how favorably the Ncore is perceived to sound to some people without altering its measurements in any fashion. By the same token the altered sonic performance may be off putting to those who have been impressed by its performance in stock form.
Bruno obviously listened to the amplifier as part of the iterative design process. What we are calling stock/cost-constrained performance, may in fact not be as sonically compromised as many see it to be.
Unfortunately, we may not be able to elicit the critical information from Bruno about what portions of the circuit do what for obvious reasons.
Scotty
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Tube Research Labs typically does not publish traditional measurements on its equipment's performance. These measurements illustrate how machines hear, not how humans hear. We probably are years away from having measurements which we can really associate to or correlate with the listenability of a device.
Fair enough. At the end of the day, how does the damn thing sound?
Nicely put, Scotty.
Quite apart from how good or not these amps sound stock---I'm sure they sound fantastic---I'm certain they can sound better. I evidently don't appreciate why thinking that is controversial.
I think when I receive my modules (should be any day now) I will first replace resistors in the feedback circuit with Vishay Z-foils just to test (verify) my hunch that noise generated by passive components in this circuit is audible. These resistors are outside the feedback loop, thus any noise they generate (all resistors generate noise) will appear nicely amplified on the output. How I will find those resistors is anyone's guess.
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Yes, I am afraid "a veil is lifted" is all you are going to get. While I adore measurements for fun....most of the time they are very meaningless as to how something sounds. Can you measure the difference between two resistors or capacitors or jacks? No, you cannot. But you can hear differences and these differences are generally agreed upon. Look at the subjective cap tests.....independently they came to the same conclusions....that the Teflon and Dueland caps are the most transparent. I am sorry, but at this point we don't have a way to measure these differences. If you want your N-Core to measure better then you better pay Bruno a lot of money to take his design to another whole level. The kinds of mods that are going to be done on the power supplies and modules will not....I repeat....will not...make the amp measure better. In fact, when I try less capacitance on the output filter, it will measure worse. However, some of the mods that will be done.......will make the amps "sound" better.
Check out the review my Maxcast on the tour listening thread. He says the N-cores do not image as wide as his Stratos amp does. This could not be related to stereo separation in any measurement way. The Stratos is a stereo amp and the N-Cores are monos. You would think the N-Cores would have better width. There are many factors that allow an amp to image very wide (outside the speakers). I am sure some of the mods that will be done on the modules and power supplies will allow a wider image. I would bet on it. Of course, there will be those that argue that the wider image is the result of some kind of phase error.
I find it amazing that the N-Cores have been available for 6 months and not one person has tried a better fuse (except one guy who said the AMRs blew up on turn on). I have some Furutech fuses that I will be listening to.
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serengetiplains, if you are lucky Mouser will have the values you need. They stock some values of Vishay SMT Z Foils
See link http://www.mouser.com/Vishay-Precision-Group-Foil-Resistors/Passive-Components/Resistors/Metal-Foil-Resistors/Metal-Foil-Resistors-SMD/_/N-8eldsZ1yzu670/?
Scotty
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I'll pop in some better fuses, Ric. What would you recommend?
Maxcast also says the mids are recessed and highs are, for lack of a better term conveying his meaning, a bit sterile. Bruno is a big fan of feedback, which I cannot see but veiling HF response in some manner necessarily. Temporal realities are temporal realities, imho.
Scotty, thank you. FYI, one can order Z-foil smds from Texas Components---any quantity, any resistance, any available tolerance (they've provided 0.005% to me in the past).
Edit: oh, I see you read my last sentence above as wondering where I might source resistors. Then you helped me find some. Thank you. What I meant by that sentence was wondering how I will find the feedback resistors on the Ncore board. Their position might be pretty obvious, but I really have no idea given the traces might be buried in some inaccessible layer.
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serengetiplains,
just curious: How long do you live with the stock amp before replacing parts?
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Phil, I'll probably let the amplifiers roast awhile to burn in, maybe a week or more depending how their sound changes. Then depending how busy I am, I'll then spend some time poking around the circuit to find critical chips and resistors. Add some time to order some resistors (they'll be the first to be changed). It's looking like a couple to three weeks thereabouts.
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thanks. Would love to see some photos of the process if you have the time and interest in doing so.
Not that I'll ever have the skill to do that kind of work, but find it interesting nevertheless.
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I'll post photos along the way to show people what I'm doing. :)
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Now you do realize that the ncores were designed to have and are reported to have no "sound", so when you say you are probably going to have a worse measuring amp, you do realize that you are merely implementing changes, not improvements, and are probably only going to color the amp (to some unknown degree at this point). Improvements are highly unlikely, changes, yes.
If you are successfully able to change the sound, then you will have ruined the whole point of the amp: high power, neutral transparent nature, blackest noise floor.
"I can't hear the amp?" .. "Oh don't worry, I'll fix that."
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Nice belief, Rclark. I don't share it.
Btw, you must mean not "highly unlikely," but "impossible." Yes?
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No, highly unlikely, not impossible. Clearly you are very experienced in this field, but I'm going with my instincts.
We'd ALL like to see if they can be improved, but they must be legitimate improvements, as in lowering noise floor even further, lowering distortion even further, etc. Chasing a sound? Doesn't seem like the right direction to be going with this amp.
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There seems to be one HUGE factor completely missing in these deliberations.... the rest of the system! For those people who have yet to hear the Ncore... myself included (mine are currently under construction) all that we have to go on apart from excellent measurements are other peoples personal opinions in their own and vary varied systems. Having read all of the reviews that I can find the general consensus to emerge on this amp would appear to be it's neutrality and a lack of any “added character”.
So why is it 'I ask myself' that there are so many people that are seemingly confident that it's the amp that could do with some modifying and improvement and not the rest of their system? Surely when dropping an amp as transparent as the Ncore into your system it could easily show up previously masked characteristics and hidden nasties' of your source, speakers, cabling, room.......
If this is the case then by modifying the Ncore you could well be trying to fix a problem in your other components by “improving” the Ncore, I'm not sure that would that be a good idea?
What we have here is a set of eternally moving goalposts, I'm not saying that it's not possible to 'improve' or 'tailor' the sound to your taste by doing a few mods but why instantly blame the amp for any shortcomings that you hear? How does the Ncore sound with the very finest sources and speakers available? I would suggest that if the Ncore consistently comes up short when paired with a good selection of the best gear out there then that would be the time to consider doing some surgery on these amps.
There are so many variables that a fair appraisal becomes virtually impossible and we all have to make do with real world tests in multitude of different set ups when attempting to evaluate the Ncore amps. This is not unique to just the Ncore amps of course.
After spending many years building my own diy hi fi and modding stuff myself the biggest lesson I have learned that you must look at your system as a whole, the Ncore will only ever be as good as the weakest link in the chain.
Anyway I wish the pioneering Ncore modders the very best of luck. :thumb:
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The point that the distortion of the ncore is much less that other components in the chain has been raised previously.
The ncore was made to be as neutral sounding as possible. Based on dozens of reviews, as well as the designer's own comments, it would seem it is extremely neutral. The distortion is among the lowest of any amp on the market.
The only way this amp can be improved is to make it even more neutral as that is the design goal as stated by Bruno...Very interesting to see how someone can make it more neutral and without any measurements, determine they have succeeded.
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The point that the distortion of the ncore is much less that other components in the chain has been raised previously.
The ncore was made to be as neutral sounding as possible. Based on dozens of reviews, as well as the designer's own comments, it would seem it is extremely neutral. The distortion is among the lowest of any amp on the market.
The only way this amp can be improved is to make it even more neutral as that is the design goal as stated by Bruno...Very interesting to see how someone can make it more neutral and without any measurements, determine they have succeeded.
Just sit back and watch. If they fail, everyone can laugh and make fun of them.
And what about soundstage and imaging? That too cannot be improved?
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Just sit back and watch. If they fail,
How will success or failure be determined?
Some people can't help messing with things. I wish all who attempt ncore mods the best of luck....I think I will leave mine alone and trust that Bruno made the most of things.
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Everything can be improved. And sometimes, good things come from just trying. If we didn't try, then we may all still be driving horse driven buggies. :lol: No offense to the Amish!
I look forward to seeing what people can do with the ncores - objectively or subjectively. :thumb:
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Yes, everything can be improved. No component is perfect. I'm quite sure regulating (or further regulating) supplies for the Ncore will bring greater clarity and see-through, as will, among other things, replacing critical resistors with Vishays.
There's no one to please in any of this but ... you, or me. Objective, subjective, measurable or not, I'll be listening to a fine amplifier, very probably made finer. But that's something I'll determine for my own purposes.
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You know... I was going to suggest, if this is feasable, perhaps you could mod your Ncores, and then send them to Mike Galusha for testing and analysis???
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You know... I was going to suggest, if this is feasable, perhaps you could mod your Ncores, and then send them to Mike Galusha for testing and analysis???
Or you can send them to me for serious listening analysis. :D
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You know... I was going to suggest, if this is feasable, perhaps you could mod your Ncores, and then send them to Mike Galusha for testing and analysis???
+1
Or you can send them to me for serious listening analysis. :D
But you still haven't even heard the stock one's....that's what the tour is for! :wink:
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+1
But you still haven't even heard the stock one's....that's what the tour is for! :wink:
Yeah, sign me up!!!!!!!!!!!!
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I might be willing to send my completed amps out for listening or testing. They will be my summer amplifiers, as my main amps (under construction---SITs, opposite end of the amplifier spectrum) will generate enough heat to make summer operation a little warm in the listening room.
Regarding inductive effects of bypassing output rails with film capacitors, I wonder if the considerable HF inductance on those leads won't actually render pulse-stream-related voltages at those capacitors something of a lower-frequency analogue waveform? When I bypassed output capacitors on my Lyngdorf, I didn't notice anything more offensive than a slight upward tilt in the HFs. The amp seemed to remain quite stable. My hunch in adding those capacitors was that they would in any event still operate at lower frequencies, which is where I wanted their contribution.
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I have seen shielding discussed as it relates to the NCore amps. This coment from Bruno on the DIY audio thread shed some light on his thoughts:
For shielding to be effective it's got to be really close to the source. Chassis make lousy shields because anything you might be trying to shield against has already coupled into the wiring inside the chassis. If you want to use the chassis as a shield you need to have feed-through filters on every piece of wire. But that's something you'd only do if there was a problem to begin with... The NC400 is pretty quiet so I'd just pick the chassis on aesthetical grounds.
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Thanks for the note, Kevin. Bruno's comment makes sense, though he's there speaking only to outgoing radiation.
My plans are to box the Ncores and the smps separately. I'll bolt two chassis together for each channel, one on top of the other, and will attach the smps just above the Ncore modules in the now separated chassis compartments. This should allow wiring as short as 2", and will fully shield the power supply from the modules and both from incoming radiation.
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My plans are to box the Ncores and the smps separately.
I was going to do this and asked before I did. I was told it will not make any difference. So, I went with the nicest, most reasonably priced chassis I could find without making one.
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Yeah, I suspect it's not a big deal. I'm going to be bypassing the smps output with some film capacitors, which will spray copious amounts of EMI that is best kept from the Ncore modules, so in my application shielding makes more sense.
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Ncore electrolytics appear to be all bypassed. Bypassing seems not such a bad idea after all, I suppose. These onboard bypasses are of course damped, and bypass only for VHF.
(http://www.audiocircle.com/image.php?id=64759)
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And here's the VDD on the comparator. It looks like the VDD lead connects to the second pin on that unused pin assembly (?) on the top of the board, which should make reading the VDD voltage relatively easy. Feeding the comparator with a squeaky clean supply looks doable. Now I'm scared because I'm tempted ...
(http://www.audiocircle.com/image.php?id=64760)
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This appears to be the comparator VDD regulator. It sits about 1" away from the comparator.
(http://www.audiocircle.com/image.php?id=64763)
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serengetiplains, If you own an oscilloscope you might look at the noise on the rails you are proposing to by-pass to see how much is there. The supply to the comparator may already be squeaky clean. Because the Ncore is an RF amplifier the by-pass caps have to be effective at lowering the impedance of the power supply at radio frequencies. If you replace these caps with ones that do not function at these frequencies due to lead inductance you could create a problem that at present does not exist.
Scotty
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serengetiplains, If you own an oscilloscope you might look at the noise on the rails you are proposing to by-pass to see how much is there. The supply to the comparator may already be squeaky clean.
It can't be, Scotty, or at least that's my opinion. I'm talking *very* clean here, something much quieter than a shared supply can offer. The comparator looks to be powered by either the +V rail for the buffers or for the gate. I would replace that with a dedicated shunt fed by two series regs in series, so a three-stage reg fed by its own transformer. That, my friend, is quiet.
Because the Ncore is an RF amplifier the by-pass caps have to be effective at lowering the impedance of the power supply at radio frequencies. If you replace these caps with ones that do not function at these frequencies due to lead inductance you could create a problem that at present does not exist.
Scotty
I appreciate the inductance problem and don't plan to remove the smd shunt caps. I'll simply add honking-big film caps with long leads spraying RFI *everywhere.* I expect to hear a sonic improvement.
Per my question a little further above, wouldn't lead inductance effectively render the pulse-train an analogue-like waveform of a lowish frequency? I see an inductor in series with two capacitors in parallel, the film add-on and the original electrolytic.
I'm not being facetious here. I've added such caps to PWM amps before (every one I've owned, in fact). I wouldn't now listen without them. The change is that large.
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The lead inductance and self inductance of the capacitor raises the caps impedance to the point that any RF present will not enter the cap in any significant quantity. The cap will look more or less like a closed door at these frequencies. It won't spray RF all over because RF won't go into in to it in the first place.
You could put together a dedicated power supply complete with double regulation, but depending on the operational frequency of the comparator circuit, the inductance of the power supply's wiring and the wiring between the first and the second regulator and the point of use may defeat your efforts. You can't spread RF circuitry all over the place adding lead inductance or board trace inductance to the circuit and have it function as intended. Usually you have to take every measure possible to minimize stray inductance at every step in the circuit to insure its stability and then you sometimes have to start adding pico-farads of capacitance here and there adjacent to components to make the circuit stable. This kind of problem can be a real SOB to avoid and a bitch to fix after it crops up.
Scotty
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I might point out that there is a very large difference between the Tact amplifiers and the Ncore. The Tact amplifier has has no error correction possible due its design. The Ncore has error correction applied and as such has a 23dB lower THD figure and correspondingly lower IM distortion figures as well.
The Tact amplifier is much more sensitive to power supply non-linearities than an amplifier with error correction. You can reap relatively larger rewards from power supply improvements because of this compared to an amplifier design with properly applied negative feedback.
Apples and oranges as it were.
Scotty
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The lead inductance and self inductance of the capacitor raises the caps impedance to the point that any RF present will not enter the cap in any significant quantity. The cap will look more or less like a closed door at these frequencies. It won't spray RF all over because RF won't go into in to it in the first place.
Thanks for clarifying; I know practically nothing about radiation, when it emits, etc. And what you say there underlies what I was questioning. You have a pulse-train current modulating the power supply, creating voltage modulations on that supply. Wouldn't those larger capacitors operate on that voltage modulation at lower frequencies? If the inductance filters radio frequency voltage modulations, wouldn't lower-than-RF modulations still get through? The larger capacitors would then work at the very frequencies at which I want them to work: in the audio realm. I'm searching here for an explanation why using film capacitors to bypass supply electrolytics on a PWM amplifier works, to my ear, and down to the bass frequencies.
You could put together a dedicated power supply complete with double regulation, but depending on the operational frequency of the comparator circuit, the inductance of the power supply's wiring and the wiring between the first and the second regulator and the point of use may defeat your efforts. You can't spread RF circuitry all over the place adding lead inductance or board trace inductance to the circuit and have it function as intended. Usually you have to take every measure possible to minimize stray inductance at every step in the circuit to insure its stability and then you sometimes have to start adding pico-farads of capacitance here and there adjacent to components to make the circuit stable. This kind of problem can be a real SOB to avoid and a bitch to fix after it crops up.
Scotty
Fair enough. I would put a very fast shunt right on the pin of the comparator. If an appropriate ground is near, that would seem to me ideal. The preregs can be placed very closely, but with the shunt being the most important, getting less than 100% from the preregs would still be good enough for me. The preregs would themselves be 1x1.5" circuit boards; wiring between the boards would be very short, probably less than a half an inch.
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I might point out that there is a very large difference between the Tact amplifiers and the Ncore. The Tact amplifier has has no error correction possible due its design. The Ncore has error correction applied and as such has a 23dB lower THD figure and correspondingly lower IM distortion figures as well.
The Tact amplifier is much more sensitive to power supply non-linearities than an amplifier with error correction. You can reap relatively larger rewards from power supply improvements because of this compared to an amplifier design with properly applied negative feedback.
Apples and oranges as it were.
Scotty
I can hear the benefit of the Ncore's feedback---I have a couple modules playing now. Their stock sound is better than that of a stock Tact, but the Ncore has a way to go to surpass what I hear with my modified Tact. The Ncores don't have quite the mud of an unmodified Tact, but I can hear a measure of it in the Ncores. The mud I'm referring to is the peculiar sound of electrolytic capacitors. I'm fairly confident the Ncore will sound better in ways the Tact did when I bypassed its supply capacitors. Fwiw, I've never heard feedback to eliminate the veiling caused by electrolytics---tube amps, SS amps, class D amps, class A amps, etc. I'd settle for 123dB on that veiling.
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Very nice close in photos! Good luck with the experiment. Hopefully Mgalusha can measure yours against his stock benchmark.
Neat :thumb:
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Thank you, R. Here's a photo of the area in question. You can see the comparator on the right. Speaker leads are on the left. The double array of solder-points is the power input connector. The power trace (one of the pair passing through the white dot) runs from the comparator up to T77, which you can barely make out near the centre at the top of the picture. I haven't traced the power source any further.
(http://www.audiocircle.com/image.php?id=64765)
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Would you be willing to take close in, hi res pics of the full surface of the amp? Could make a cool poster.
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And a few more of that corner, a bit closer.
(http://www.audiocircle.com/image.php?id=64767)
(http://www.audiocircle.com/image.php?id=64768)
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Would you be willing to take close in, hi res pics of the full surface of the amp? Could make a cool poster.
Sure, I could do that tomorrow. Its nearly impossible to see the traces on these photos, so I don't think posting a high-rez picture would do a disservice to Bruno. If anyone has a concern, please let me know.
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Here you go!
(http://www.audiocircle.com/image.php?id=64799)
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Saved. :thumb:
Which camera are you using for that? Those are just excellent close ups. And also fascinating that those tiny caps are also bypassed as well.
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I bypassed some output capacitors today. To reduce inductance, I match two capacitors, tie them together, then run four twisted wires, two +/– to the left side, two –/+ to the right. This keeps lead length smaller (about 1" per lead depending on the circumference of the cap, = 2" per capacitor).
I'll hold off on reporting much detail right now. The capacitors I added are new teflons that need time to break in, the DAC is a DragonFly (ok, but not great), I only have one channel bypassed, I want to add bridged modules, the amps and power supplies are still breaking in, etc. That aside, adding the teflons did what I expected. Though I hear HF edge (some of which is attributable to amp break-in, teflon cap break-in, jittered output from the DragonFly), the amp hit moments of shocking realism. When I first turned the amp on (left channel bypassed, right channel stock), I thought I possibly destroyed my tweeter in the L bypassed channel. I was playing a song with a long lead-in, bass-lower-mid riff and could hear nothing from the tweeter. After a jolt of anxiety wondering how I could have ruined my tweeter (a ribbon), I realized the tweeter was fine. What triggered my wondering was I could sense differing HF pressure levels from L and R channels, with the L channel dead. The difference, I take it, was some form of noise.
Here's another interesting observation. I can run the amp flat out and the L channel woofer (a mere 4" job) doesn't flap and remains well-controlled. The sound is clear and undistorted. I wanted to turn up the volume more, but couldn't---the amp was maxed. The right channel woofer, for its part, began hitting its excursion limit somewhere near full volume. When it does, it emits a nasty blurrp. Not so the L channel.
The HF edge will reduce with time, particularly with a good DAC, better attention to wiring. A good NOS seems a good fit here. It will be interesting to hear how bridged operation affects the sound. Bridged should reduce power supply noise further (nasty electrolytic DA, among other things).
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Saved. :thumb:
Which camera are you using for that? Those are just excellent close ups. And also fascinating that those tiny caps are also bypassed as well.
It's a Panasonic Lumix portable, the cheapest way I could get a Leica lens. It puts out 10MB raw files. I think the one I posted was a 4.7MB jpg compression, which I'm sure this website reduced further.
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Wow, this is one seriously good amplifier. Really good job, Bruno! :thumb:
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And also fascinating that those tiny caps are also bypassed as well.
I think all the electrolytics on the board may be bypassed. I haven't really looked, but it would seem good practice to boost a little more cap action for HFs.
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Here's the temporary bypass-capacitor wiring.
(http://www.audiocircle.com/image.php?id=64800)
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And with that, correction, 5.25" woofer, I'm getting 30-40Hz bass, a bit in the 20s, moreso than when the amp was unbypassed. That's some woofer control.
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I was looking at the pin-out for the comparator chip. It has a Vss. Google tells me that's a negative supply? It then looks like the buffer supplies supply the comparator, which looks to operate differentially. Perhaps it must? Cough.
(http://www.audiocircle.com/image.php?id=64801)
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Can you give more details of your bypassing? What power supplies were bypassed and with what values of what brand of Teflon caps are you using? Are you orienting the outside foil to the the lower power supply polarity or to ground? I find the outside foil direction to be very important.
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That pin out is for a PIC micro controller from Microchip. It has a comparator built-in but is really a fully programmable little processor. I hope it isn't in the analog path. Maybe it is doing some fancy feedback and controlling the output FETs.
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And with that, correction, 5.25" woofer, I'm getting 30-40Hz bass, a bit in the 20s, moreso than when the amp was unbypassed. That's some woofer control.
You measured that change in LF response?
Anand.
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Can you give more details of your bypassing? What power supplies were bypassed and with what values of what brand of Teflon caps are you using? Are you orienting the outside foil to the the lower power supply polarity or to ground? I find the outside foil direction to be very important.
I bypassed one output electrolytic on what I assumed was each output rail. I grabbed and used a few caps just to test proof of concept. For the final implementation, I generally want the most, best capacitance in the least amount of space, with foils oriented as you suggest.
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That pin out is for a PIC micro controller from Microchip. It has a comparator built-in but is really a fully programmable little processor. I hope it isn't in the analog path. Maybe it is doing some fancy feedback and controlling the output FETs.
Thank you, kc. I think that chip is in the analogue path, perhaps functioning also as a gate driver, but I barely know how this amp works. The unused connector on the top of the amp seems to be for programming that chip, which might be a place to install good regulators. I suspect the chip is involved in the feedback loop.
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Thank you, kc. I think that chip is in the analogue path, perhaps functioning also as a gate driver, but I barely know how this amp works. The unused connector on the top of the amp seems to be for programming that chip, which might be a place to install good regulators. I suspect the chip is involved in the feedback loop.
If you look at section 8 of the data sheet it is for control and monitoring:
The microprocessor has three main functions: to provide an interface for controlling the amplifier, to
monitor the supply voltages in order to prevent spurious operation during power up/down and to
detect error conditions.
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If you look at section 8 of the data sheet it is for control and monitoring:
The microprocessor has three main functions: to provide an interface for controlling the amplifier, to
monitor the supply voltages in order to prevent spurious operation during power up/down and to
detect error conditions.
Here is a description from the data sheet.
(http://www.audiocircle.com/image.php?id=64825)
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You measured that change in LF response?
Anand.
No. I gave only quick listening impressions.
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Back to the comparator for a moment. That chip performs probably the most important function in the amp, and as such would be the most important source of nonlinearity and distortion. A little jitter on that delicate oscillator and ...
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Here are a few paragraphs from one of Cyril Bateman's articles talking about electrolytics. In the Ncore, electrolytics are in effective series with the output. The output FETs connect the output from these capacitors to one's speakers. One is therefore listening, at all times, to electrolytic capacitors. For me, electrolytics are the weakest link in the audio chain.
(http://www.audiocircle.com/image.php?id=64826)
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And with that, correction, 5.25" woofer, I'm getting 30-40Hz bass, a bit in the 20s, moreso than when the amp was unbypassed. That's some woofer control.
You measured that change in LF response?
Anand.
No. I gave only quick listening impressions.
Wow. I am humbled.
Anand.
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serengetiplains, I am attempting to put your listening impressions into to some kind of context.
How many operating hours are on your modules? Also have you considered doing further listening tests using a mono signal or only one stereo channel and listening to the sound of the modded and unmodded amplifiers in an A/B comparison? This would eliminate the variable of attempting to evaluate the sound of the modded amp with a signal that differs from the one being fed to the unmodded amp.
If the sound of the basic unmodded Ncore was found wanting when compared to a TACT amp a substantial amount of the HF short coming could be attributed to the electrolytic power supply caps not being fully broken in. It could take perhaps 300hrs to fully break the power supply caps as well as the output filter components.
A subjective phenomena I have noticed when listening to stereo systems is that when the high frequencies above 10kHz are are extended or improved, there is also an improvement in bass definition and apparent extension. When in fact however, there has been no actual change the bass at all only the highs have been changed. The bass can go from being muddy sounding and lacking in extension to being tight, well defined and appearing to have another half octave of extension.
It would also be helpful if you listed your system components, we know you have a modded Tact amp and that is all. could you provide a link to the rest of Cyril Bateman's article it looks like interesting reading.
From the part you quoted, it appears that he referring to consequences of using an unpolarized electrolytic capacitor as a coupling cap with no biasing voltage present. This is certainly one of the worst case applications for an electrolytic cap that might be seen in consumer electronics.
Scotty
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Scotty, I'm listening through AAD 7001 speakers with upgraded crossovers. They have a passive radiator on the back, and claim a 25Hz frequency response. I've been hearing some of that lately. Anand, the sub-40Hz is down in level, but I wasn't straining to hear what I reported. The rest of my system is a Mac Mini and an Audioquest DragonFly DAC, a few pieces of cheap wire and some power conditioners (two regenerators in series feeding the amps).
The right channel is stock, so I've been flipping between stock and modified. It's a quick and easy test. Differences between the channels are easily heard.
I've heard bass tonality change from a change in HF response. This is not all that's happening here. From my above reference to woofer excursion, I infer that bass frequencies are also being affected. The L woofer (bypassed amp) is visibly and audibly better controlled than the R. Thirty years ago I owned a Marantz amplifier that had peak-LEDs on it. After I bypassed electrolytics on that amp with some teflon caps, I got a full 30 degrees further movement of the volume control before those LEDs lit. The lesson of that experiment has stayed with me.
I think the Bateman series of articles is out of print. I sourced my copy at the local university library. The articles ran from Jul-Dec in Electronics World.
And yes, the electrolytics on the Ncores are still breaking in---the amps have been plugged in for maybe 48 hrs. I've learned to hear the sonic signature of new capacitors---fwiw, teflons are the absolute worst and sometimes sound dreadful when first used. Because I have a stock and modified Ncore in my system now, I can hear relative differences despite the entirely moving playing field this setup represents.
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I think I have found the articles you referenced online.
http://www.scribd.com/doc/2610442/Capacitor-Sound
What is interesting is that he found that bypassing electrolytic capacitors with film shunt capacitors gave no useful reduction in distortion and the lowest distortion electrolytic power supply caps were a pair series connected bi-polar capacitors.
Fascinating reading.
Once again there appears to no measurable reason for an observed sonic improvement, it figures.
For what it's worth I have also heard improvements from bypassing electrolytic power supply caps with film types.
Scotty
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Here is a description from the data sheet.
...
What I shared was from the NC400 data sheet, not the PIC.
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I think I have found the articles you referenced online.
http://www.scribd.com/doc/2610442/Capacitor-Sound
What is interesting is that he found that bypassing electrolytic capacitors with film shunt capacitors gave no useful reduction in distortion and the lowest distortion electrolytic power supply caps were a pair series connected bi-polar capacitors.
Fascinating reading.
Once again there appears to no measurable reason for an observed sonic improvement, it figures.
For what it's worth I have also heard improvements from bypassing electrolytic power supply caps with film types.
Scotty
That be the series, Scotty.
There's a part of me that prefers tube amplifiers for the sole reason they can be built entirely without electrolytics.
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Speaking of (almost) electrolyticless amplifiers, ahh:
http://purityaudiodesign.com/ultra%20gt.htm
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Back to the comparator for a moment. That chip performs probably the most important function in the amp, and as such would be the most important source of nonlinearity and distortion. A little jitter on that delicate oscillator and ...
Based on:
If you look at section 8 of the data sheet it is for control and monitoring:
The microprocessor has three main functions: to provide an interface for controlling the amplifier, to
monitor the supply voltages in order to prevent spurious operation during power up/down and to
detect error conditions.
the PIC is not acting as a comparator nor is it part of the analog path at all. It only handles supervisory functions. It should be fed from a separate digital supply and use a dedicated digital ground. Extra bypassing won't hurt anything but it shouldn't change the sound in any way.
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Thank you, kc. Perhaps the comparator is discrete, in which case I won't be tampering with it.
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I have bridged mode up and running. 8) It's too early to say anything much about the sound, but it does sound different, and I think I like it.
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So, you appear to be the first to assemble a bridged setup! Yay!!!
Are you using 2 SMPS for the 2 NC400's? 150 nf cap?
Thanks a LOT for any info on this and your listening impressions.
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Yes, up and running! I'm using a single smps. My reasoning is that psu noise cancellation is probably best with a single supply as, all other things being equal (they never are), I want the same noise signal on both amps to allow summing of such on the output. But with two Ncore modules drawing from a single supply, that supply will be forced to operate at higher currents, therefore creating more noise to that extent. Two smps might sound better, but at the volume levels at which I normally listen, I don't think that would be the case.
In any event, bridging sounds to me to be an improvement. The effect I heard, on initial impression, is subtractive---as in, hey, something's missing. What's missing is not detail, not power, not resolution; it must be noise. Bridge mode brings greater subtlety, better definition, more obvious power. I like what I hear, but these are impressions based on only a short period of listening to non-bridged mode. I've only had these modules a few days, so my aural memory of non-bridged mode is not very strong. Let's put it this way: I don't hear anything I don't like that I feel has been added by operating the Ncores in bridge mode. I would be able to identify something like that.
Re the cap, I'm using what I had quickly on hand, which happened to be a 0.068uF cap. I'll experiment later with a larger cap, toward the 0.15uF value Bruno recommends.
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I'm enjoying the single monos very much but, with 81dB speakers, it's hard not to think about more power.
Is there somewhere where the single/dual SMPS for bridging is discussed, recommended?
Thanks!
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I certainly don't need more power myself, though I do hear a benefit of having more power in reserve. The music emerges more relaxed, if you will.
I don't have a clear understanding of the topology of this amplifier yet, but it seems to me that bridging should give greater power supply noise reduction. By power supply noise, I mean anything entering, riding on or produced by the main output or any of the power rails---whether RFI/EMI picked up from god knows where, voltage variations emitted by the switching elements of the supply, variations created by current draws passing from a positive-impedance, dielectric absorption voltages from the ugly output and supply electrolytics, various resonances and instabilities---all of which exist dynamically in a complex state of constant movement and flux (simplistic sine-wave analyses don't come close to modeling this stuff). I'm speaking here of the entire gamut of AC existing on the power rails, which should be pure DC. Subject to limited feedback reduction, that noise will pass 1:1 through the Ncore FETs into your speakers into the air into your ear.
This is what I call power supply noise. It is always present and always affects any component operating where- and however. This noise, because largely dynamical, cannot be heard by placing one's ear at a tweeter. It's a kind of dynamical noise that veils the signal.
Subject to having a perfect DC supply that remains perfectly DC always (hence zero-impedance and absolutely linear, with perfectly ideal components), not to mention having a perfect amplifier, the only way to reduce this noise beyond reductions wrought by feedback or component quality is to have that noise cancel itself by operating differentially. It seems to me that bridging offers better differential noise cancellation than a mono amp can attain. One of the reasons this amp sounds so good stock is the considerable attention Bruno gave to differential operation. From what I can tell, the amp operates differentially from input to out.
Fwiw, bridging sounds quieter to me, more relaxed, less edgy in a kind of edge I associate with noise. I want to listen a little more, but merely my listening today has convinced me I will go with bridging using a single supply. I may someday hook up another supply to compare single- vs. dual-supply, but theoretically, one wants the very same noise signal on the + and – legs of the speaker terminal. That voltage will produce no signal in the driver. A single supply theoretically gives a closer approximation to the same noise signal on the output. Because the drivers are operated push-pull, that noise will cancel. What remains to produce sound is (more) the signal.
Also remember that current modulations in each of the supplies---the output, gate and buffer supplies---will produce noise as I've briefly described above that will intermodulate in complex ways with the operation of those supplies one to another. Reducing noise in any of the supplies will reduce that intermodulation, leading to cleaner DC rails for all active components in the amp.
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serengetiplains, If I understand your most recent post, you are saying that Bruno advocates using a .15uF cap for a bypass of the positive and negative power supply rails on the module,correct ?
If so it should be possible to find a very small form factor capacitor per Cyril Bateman's recommendations for a very low inductance, low distortion cap. In as much as the cap shouldn't have to withstand more than 150volts, even a .15uF cap should be small enough that you could shorten the leads to the point that the lead inductance is at least the same or less than the intrinsic inductance that cap has due to its type of construction. It might be possible to actually have the cap function as usable bypass for reducing HF and RF noise if the total self inductance can be kept low enough. What a concept. Does Bruno have anything more specific for a recommendation for this cap other than just the value. I am fishing for a brand or film type recommendation.
Scotty
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Scotty,
They recommend the small cap hot output to hot output when bridging.
http://www.audiocircle.com/index.php?topic=106827.msg1102629#msg1102629 (http://www.audiocircle.com/index.php?topic=106827.msg1102629#msg1102629)
Tom
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Thank you, Tom. That's how I've connected my Ncores in bridge mode (though currently using a 0.068uF cap).
Somewhat OT, for those wanting a good bypass capacitor for cheap, try these:
http://www.ebay.com/itm/0-5uF-250V-0-5-K71-7-Polystyrene-capacitors-Lot-of-50-NOS-/251060469200?pt=LH_DefaultDomain_0&hash=item3a745ebdd0
These capacitors (and this comment pertains only to the 0.5uF varieties) measure incredibly. I have a capacitance meter that measures DF to 6 decimal places. You will notice from Bateman's article that DF roughly correlates with DA which strongly correlates with level of capacitor distortion. The above caps typically measure 0.000005 DF. I've measured quite a few at 0.000000 DF---off the scale! A good teflon typically measures 0.000010 to 0.000020, sometimes less. Good polypropylenes typically measure 0.0000150 to 0.0000300. Mylars, which are used as the output filter caps in the Ncore, measure 10 to 20X this. Mylars are also polar (not polarized), so distort worse for that reason also. I'll be bypassing these caps in the Ncores (I'd rip them out if I could do so without ruining the amp).
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Something that may be poorly understood about switching power amps like the Ncore. The Class D amplifier pulls current from the power supply at the switching frequency not at the audio frequency present at the analogue input. The higher the power the amplifier supplies to the load the higher the current demanded from the power supply. When power supply delivers these higher current levels to amplifier this is exactly the same as turning up the amount of watts emitted by a RF transmitter at its antenna.
The power supply wiring is the transmitter antenna. This is the predominant noise in the box and its loudness is a function of the power delivered to the loudspeaker. This is also true for a conventional amplifier, the difference being that the frequency varies as a function of the audio input. The power supply wiring can also radiate HF noise and the power supply can also ring at high current levels.
The secondary source of noise is the SMPS switching frequency. It would be very interesting to look at the voltage output of the SMPS on an oscilloscope. This would show any and all noise contaminating the DC power supplied by the SMPS.
Scotty
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The secondary source of noise is the SMPS switching frequency. It would be very interesting to look at the voltage output of the SMPS on an oscilloscope. This would show any and all noise contaminating the DC power supplied by the SMPS.
If I can scare up some time I'll poke at mine with the scope and take some photos. I don't have a DSO, so it's camera on the tripod for oscilloscope images. But I do like my analog Tek scope, 400Mhz, so it sees HF noise pretty well.
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Is it possible you can compare the noise on the + and – rails? If that noise is not a mirror image one rail to the other, bridged operation will I think of necessity give better PSRR.
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Thanks Mike, any data is good. I have very little experience with SMPS. I get how one can see a 60Hz or 120Hz charging frequency show up and add to raising the noise floor via hum. What is unclear to me is how the SMPS switching frequency gets suppressed to the same degree. It would seem as though you would need to incorporate a high current L or TT filter to suppress the switching frequency adequately.
Scotty
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Also Mike, can you measure power supply noise when playing music through the Ncore? How the overall noise changes under dynamic conditions would I think be telling. Also telling, I think, is whether noise signatures on the + and – rails change relative to one another in dynamic conditions. That might be a difficult task with a camera, but you might be able to see such differences, if there are any, and report what you see. If you can and if you have the time ... Cheers
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Something that may be poorly understood about switching power amps like the Ncore. The Class D amplifier pulls current from the power supply at the switching frequency not at the audio frequency present at the analogue input. The higher the power the amplifier supplies to the load the higher the current demanded from the power supply. When power supply delivers these higher current levels to amplifier this is exactly the same as turning up the amount of watts emitted by a RF transmitter at its antenna.
The power supply wiring is the transmitter antenna. This is the predominant noise in the box and its loudness is a function of the power delivered to the loudspeaker. This is also true for a conventional amplifier, the difference being that the frequency varies as a function of the audio input. The power supply wiring can also radiate HF noise and the power supply can also ring at high current levels.
The secondary source of noise is the SMPS switching frequency.
Yes, let's call that current a pulse current in the shape of a PWM signal. Tell me if I'm off here with what I see. That pulse current will create voltage fluctuations given the non-zero impedance of the supply, and those fluctuations will more or less mimic the PWM timing of the pulse currents. It seems to me those voltage fluctuations would themselves approximate square waves (a very distorted, possibly more analogue version of which, surely). As I understand them, they are but the music signal plus an appreciably high level of harmonics. An audio signal is therefore travelling inside of those currents, albeit a signal with a nasty amount of noise. Those harmonics are themselves recycled via the output filter, allowing the music signal to emerge from the amplifier output. I'm not disagreeing with anything you're saying above, but am wondering if I'm picturing this supply activity properly.
Re radiation, is it positive impedance on any part of the supply rail that causes radiation? Why does a circuit trace radiate, Scotty?
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You have asked a question without a very simple answer. In the case of the ClassD amplifier you have the transmitter carrier frequency which is the switching frequency and the amplitude modulation of the carrier which is done by the audio signal fed into the amplifier. It's an AM transmitter and depending on the effectiveness of the output filter, the speaker cables can be the transmitters' antenna. I could easily pick up the output of my TA 3020Tripath amplifier on a hand held AM transistor radio when I held it near the speaker wires.
To put it simply the higher the frequency you try put into a wire and have it go from point A to point B the harder it is to keep inside the wire. If the frequency is high enough it won't really be in the wire at all, it will exist entirely as a field around the wire at this point and a lot of energy will be radiated into space.
For example, the radar transmitter of a warship is located somewhere in the bowels of the ship below decks. The radar mast is located in the superstructure of the ship. The transmitter is connected to the antenna with highly polished copper tubing that cannot have any dents or dimples in it or you will have a short. The copper tubing is acting as a highly efficient wave guide for the radar signal that you wish to propagate from the antenna topside. The signal exists as a field that is contained in the tubing. Weird huh?
For the amplifier, the shorter the traces are, the less effective they are at either radiating noise or picking up noise that is present in the environment. You also have a much easier time building a high speed circuit if you keep the circuit traces short and the board small. The Ncore module is a textbook example of how to do it right. If the power supply wiring is kept as short as possible in the Ncore the ability to radiate noise is curtailed because the antenna is smaller.
Hopefully this simplistic explanation makes some kind of sense, I don't write textbooks for a living.
Scotty
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That's an excellent explanation, Scotty. It works for me. And this stuff truly is weird sh*t. It reminds me of an anecdote regarding Einstein. Einstein was sitting at his desk in Princeton when an excited grad student burst into his office explaining his excitement over some new collider and how we will know more blah de blah. Einstein looked up at him and said, "I just want to know what an electron is."
Yes, Bruno's board is fantastic. It's the smallest board I've seen, which helps everything including allowing a tighter, more precise feedback operation.
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Thanks Mike, any data is good.
Only and only if it's good data. Otherwise I'd rather have none. :wink:
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I should have said that I trust that any data Mike is willing to share will be worth having and represent a correct use of the test equipment he has available to him.
Scotty
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I should have said that I trust that any data Mike is willing to share will be worth having and represent a correct use of the test equipment he has available to him.
Be sure that if I don't think the data is valid, it won't leave my basement. :) That said, I've been fooled before but hopefully I've learned over the years to not be fooled as easily.
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One could also, while the amp is playing, capacitively couple the + and – power rails to a junction that is used as the input to an amplifier or digital-capture device. One could then hear and see what's happening on each rail, and even listen/capture the difference component between the rails.
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I think there's a song somewhere like that, I won't be fooled again. :lol:
Scotty
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I think there's a song somewhere like that, I won't be fooled again. :lol:
Scotty
Who would sing it? :?
Maybe as song about low lying fruit, not by any means strange.
When all you have is a hammer, we tend to see everything as the thumb...
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To attach large bypass capacitors to the output electrolytics, I have decided I will use 8 strands of small-gauge litz magnet wire. Two matched capacitors will be used as a single bypass cap, with two litz wires per capacitor lead, wired as follows (substitute two strands of litz wire per strand of wire in the photo):
(http://www.audiocircle.com/image.php?id=64886)
(http://www.audiocircle.com/image.php?id=64887)
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Who would sing it? :?
They did, actually. http://www.youtube.com/watch?v=SHhrZgojY1Q
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Larger bypasses will be wired as above. Smaller bypasses (say, 0.1uF and 0.01uF) will be wired with their leads directly soldered to the electrolytic terminals. Total number of bypass capacitors will therefore include a minimum of three capacitor values to spread any inductive resonances I'm creating. I may have to ditch the aluminum bottom plate to best pull this off. That's workable. There's a small (what looks to be) heat sensor that fits snugly into the bottom plate, but I'm supposing that sensor doesn't communicate with the amp unless the sensor gets too hot. The output FETs will be well heatsinked, so I'm unconcerned about the sensor.
(http://www.audiocircle.com/image.php?id=64888)
(http://www.audiocircle.com/image.php?id=64889)
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Here's a clearer representation of my not-quite-inductance-free capacitor wiring. Cough.
(http://www.audiocircle.com/image.php?id=64890)
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Are you going to re-measure what was a superb measuring amp?
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I doubt I will, JT. That's assuming the amp works when I'm done with it.
My only interest is better sound, and if I attain that to my satisfaction, I'll, uhh, probably look for more ways to get more of that satisfaction. I get really bored with a certain level of amplifier performance. The Ncore is to me good, but like any amplifier with normal-grade parts and less-than-stellar power supply regulation, it lacks a certain mmm-wow.
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serengetiplains, what value, voltage and film type are the caps that you're are going to use.
Generally the bigger the cap the lower it's resonant frequency will be. If the resonant frequency of the cap falls below the frequency range you are trying to affect the bypassing effectiveness will be greatly diminished. As an example I called Hovland a few years ago when they were still in business and got Bob Hovland on the phone to ask him what the resonant frequency was of an 8mfd 100 v MusiCap. Bob replied that it was 140kHz. I went ahead and bypassed the 4 pole Jensen caps in the power supply of my Tripath amp anyway even though the switching frequency was over 700 kHz. It made a small worth while improvement but I don't believe it was due to noise reduction. I think it might have had more to do with having a small amount of very low impedance energy storage available for reproducing the leading edge of the waveform. There certainly wasn't an adequate amount of power stored at 54volts to run the amp for any significant period of time.
If you are actually trying have an effective bypass at the amps switching frequency the smaller caps will have to have leads that measure in length in the Millimeters or the lead inductance will defeat your purpose.
By the way have you thought about replacing the wiring that came stock with something better,that would surely be a quick and simple upgrade path.
Scotty
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Here's another tweak idea. The output FETs probably operate more linearly when instantaneous heat is removed as quickly as possible from the devices. The stock TO-220 insulators look to be ceramic (aluminum oxide) which, per Aavid, has a thermal conductivity of 15.06 W/mK at 75° (167° F) (8.71 BTU/hr-ft° F). Compare to beryllium oxide at 221.94 Wm-1 °C-1 (128.2 Btu/hr.ft.°F).
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What also has to be considered is the operating temperature curve of the output MOSFETs. There will be a temperature zone where the FET is at its most linear and that is not room temperature. In the case of my old Tripath amp the heatsink that came with the EVAL board was a little bit of too much of a good thing. Even though the amplifier was left on 24/7 the output MOSFETS were below their ideal operating temperature. The amp sounded better after it had been playing music for about 10 min. than it did when you first pressed play on CD player.
Scotty
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serengetiplains, what value, voltage and film type are the caps that you're are going to use.
Generally the bigger the cap the lower it's resonant frequency will be. If the resonant frequency of the cap falls below the frequency range you are trying to affect the bypassing effectiveness will be greatly diminished. As an example I called Hovland a few years ago when they were still in business and got Bob Hovland on the phone to ask him what the resonant frequency was of an 8mfd 100 v MusiCap. Bob replied that it was 140kHz. I went ahead and bypassed the 4 pole Jensen caps in the power supply of my Tripath amp anyway even though the switching frequency was over 700 kHz. It made a small worth while improvement but I don't believe it was due to noise reduction. I think it might have had more to do with having a small amount of very low impedance energy storage available for reproducing the leading edge of the waveform. There certainly wasn't an adequate amount of power stored at 54volts to run the amp for any significant period of time.
If you are actually trying have an effective bypass at the amps switching frequency the smaller caps will have to have leads that measure in length in the Millimeters or the lead inductance will defeat your purpose.
By the way have you thought about replacing the wiring that came stock with something better,that would surely be a quick and simple upgrade path.
Scotty
Scotty, I understand that any bypass capacitors will operate in the lower KHz region depending on lead inductance, meaning they won't affect switching-related artifacts. Per your experiment, and experiments I have performed with class D amps (Tact, Tripath), bypassing to my ear creates obvious audible effects, the overall sum of which I find quite pleasing.
I suspect bypass capacitors help shunt DA recovery voltages to ground. DA is generally modelled as follows:
(http://www.audiocircle.com/image.php?id=64891)
You can see from the model that capacitors release spurious voltages related to the original input (charging) voltage at frequencies determined by the parallel RC combinations, the R indicating, I think, a lower frequency given the lagged release. Here is a graph that purports to show recovery voltage/time after release of the original charging voltage. Nasty stuff.
(http://www.audiocircle.com/image.php?id=64892)
How this data reflects a working circumstance is beyond my guessing abilities, except perhaps to say this: DA recovery voltages will carry a frequency related to the overall peak charge/time of a capacitor. I suspect that the pulse-current on the output of the Ncore (or any class D amplifier) can be decomposed into lower (including audio) frequency and higher (including switching) frequency components. This decomposition is performed quite handily by the LCR filter on the output. I don't see why a similar decomposition cannot be performed prior to the output, with L provided by the capacitor leads. This would suggest the capacitor can operate at audio frequencies despite the high switching frequency, thus removing audio-frequency noise from the output rails. This is actually what I hear.
Fwiw, here are a few charts I created to test DA recovery voltages. I used a good DMM with a 10Mohm input, which is too low for consistent data for capacitors of differing values. But the charts at least give some correlative evidence of DA effects, particularly for same-size capacitors.
(http://www.audiocircle.com/image.php?id=64893)
(http://www.audiocircle.com/image.php?id=64895)
(http://www.audiocircle.com/image.php?id=64894)
I doubt I've answered your question to anyone's (including my) satisfaction, but what we need is some explanation, however tentative or cursory, to give some insight into what's happening.
I will use 1000V 2.2uF Solen metallized teflons for the large bypasses (smallish!), and 100V 0.1uF and 0.01uF film/foil teflons for the on-board bypasses.
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What also has to be considered is the operating temperature curve of the output MOSFETs. There will be a temperature zone where the FET is at its most linear and that is not room temperature. In the case of my old Tripath amp the heatsink that came with the EVAL board was a little bit of too much of a good thing. Even though the amplifier was left on 24/7 the output MOSFETS were below their ideal operating temperature. The amp sounded better after it had been playing music for about 10 min. than it did when you first pressed play on CD player.
Scotty
Good point, and thank you. I guess I'll test this little tweak separately by listening. I suspect the average heat will not change; it's the instantaneous heat spikes I'm going after.
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A better model of DA is the Cole-Cole parameter method (graphics below from here: http://www.cktsim.org/modeling/da.pdf ). This model characterizes DA as follows:
(http://www.audiocircle.com/image.php?id=64899)
Z[A] is graphed as follows:
(http://www.audiocircle.com/image.php?id=64900)
... leading to a capacitor model that includes DA, which looks like this:
(http://www.audiocircle.com/image.php?id=64901)
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Per Parts Connexion price list it looks like you've got about $800 in 4 caps for "large" 2.2 uF bypasses. Are these caps superior sounding to foil and film caps such as V-caps CUTF and TFTF series. As a less expensive alternative I might be tempted to try the Robert Hovland SuperCaps,2.2 uF 200v polypropylene film and foil at $29 a piece. Obviously I am biased towards the Hovland caps due to past experiences with them.
Scotty
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Per Parts Connexion price list it looks like you've got about $800 in 4 caps for "large" 2.2 uF bypasses.
:o
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I measured one Hovland capacitor in the sheet above. It looks to have a good DA rating. Teflons are expensive, but I find their use to give good value sonically---rather more than expensive cabling. If you look at my DA test results above, you can see on line six a Customs Electronics 1uF tin/teflon cap. Its DA recovery voltage measured ave. 0.170V thereabouts, which is very low for a 1uF cap. The Solens, for their part, measure DF quite closely to the CustElec cap, suggesting a similar DA. This is, I think, due to their use of a 1000VDC dielectric. Generally speaking, for two capacitors of the same design having different DCV ratings, the higher DC-rated cap will give a lower DA figure. And the Solens being metallized, they're physically smaller than a tin foil variety. The trade-off, here, is between lower inductance and higher ESR (and whatever else differentiates tin-foil from metallized caps).
On the second page of that chart of results, take a peek at line 5, showing a 10uF 100V Mylar. Its DA recovery voltage? A whopping 31V! That's 180X that of the CustElec teflon.
I think the caps in the output filter on the Ncore are Mylar.
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I have a found another take on DA. It appears that in some cases what is measured as DA may be another phenomena that is related to capacitor construction.
Here are links to the article describing the phenomena.
http://www.keith-snook.info/capacitor-soakage.html
http://www.keith-snook.info/more-capacitor-soakage.html
Scotty
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Those are excellent links, Scotty. I skimmed one of them now and will read them more carefully later. It looks like the author has identified a mechanism that correlates in important ways with what is observed in capacitor recovery voltage. Notice the last document I posted in Reply 155 above. In that test, I subjected a Jensen 3.3uF PIO capacitor to successively longer charges to measure the resulting recovery voltage. The recovery voltage approximately stabilized to a peak, with subsequent +/– fluctuations, after about an hour's charge.
This increase is consistent with the author's thesis, as are phenomena of capacitors singing, of noise generated by tapping a signal-carrying capacitor with a pencil, etc.
One source of expansion/contraction is likely trapped air in the windings. An oil capacitor would have little or no such air, firming the capacitor considerably.
I suspect there's more happening than an expansion/contraction of the dielectric. Teflon is quite a soft dielectric---squishy---so it would seem most prone to dielectric compression. Yet teflons measure consistently better on recovery-voltage tests.
I also ran some tests testing the speed at which peak recovery voltage is attained in the various capacitors I tested. Here are the results:
(http://www.audiocircle.com/image.php?id=64909)
(http://www.audiocircle.com/image.php?id=64910)
Notice the first capacitor. That cap is a paper-in-fluorinert cap I had wound for me. True to form with other oil (wet) capacitors, recovery voltage is extremely high. But its recovery time is *fast.* Compare its results with results for other PIO caps on page 2.
Fluorinert is essentially liquid teflon. The variety I used for the PIO cap has a dielectric constant of 1.8, 10% lower than that of teflon. I suspect the liquid nature (reducing dielectric compression and possibly allowing some form of DA-voltage cancellation through physical movement of the molecules), combined with the low Dk (= low DF and low DA), allowed the fast voltage recovery. J'speculate.
Fwiw, these capacitors bettered teflons in listening tests I performed. They were really clear.
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You might measure the DA of the new series of Nichicon solid polymer aluminum electrolytic capacitors.
While they have substantial leakage current which will render them unusable for some applications, they can make a pretty good coupling cap when a polarizing voltage is applied. I am using these for the output coupling cap in my preamp and the DC blocking capacitor in the feedback loop of my amp.
I think they are substantially more transparent than either the BlackGate FK series or the Non-polar NH series.
Here is a link to the part no. I used
http://www.digikey.com/product-detail/en/RR71C331MDN1/493-3718-ND/2207254
I think I noticed the presence of surface mount capacitors, if they are not already organic polymer tantalums this might be good upgrade. Organic polymer tantalums can have very low ESR as well as sounding almost as good as the solid polymer electrolytics, . They are spendy though running between $2 and $10 apiece with some over $10. Here is a link to the Mouse http://www.mouser.com/Passive-Components/Capacitors/Tantalum-Capacitors/_/N-75hqv?No=100&P=1z0ylhg
Scotty
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I'll get some of those and will check them, Scotty.
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Here are some pictures of the interior of an Ayre VX-R, which sells for something like $15K. I think they show what Charles Hansen thinks of bypassing electrolytics. I think the smaller yellow caps are teflons. The white may be teflons also, I can't remember.
(http://www.audiocircle.com/image.php?id=64913)
(http://www.audiocircle.com/image.php?id=64914)
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And here is the MX-R mono version.
(http://www.audiocircle.com/image.php?id=64915)
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And here is the conrad-johnson Mini-ART and GAT interiors, respectively. I think the Mini-ART uses polypropylene and teflon caps in its power supply. The GAT uses teflon exclusively. Earlier models of the ART used styrenes, I believe. No or few electrolytics in the B+ supplies (I see one in the GAT photo).
(http://www.audiocircle.com/image.php?id=64916)
(http://www.audiocircle.com/image.php?id=64917)
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Here's the Purity Ultra GT. Polypropylenes.
(http://www.audiocircle.com/image.php?id=64918)
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The Lyra Connoisseur. Polypropylenes, I believe. Lots of inductance on those power supply wires. Any guesses why the design as such?
(http://www.audiocircle.com/image.php?id=64919)
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Regarding electrolytics, because they're polar (not in the Mylar sense), I suspect voltage pass-through and recovery voltage effects differ depending whether the voltage is traveling from + to – or from – to + ... in some form of asymmetrical filtering. If true, it would be bad news for electrolytic-heavy differential +/– supplies as found in the Ncore. Those supplies by definition could not contain mirror or approximate mirror versions of noise on the respective + and – rails, diminishing differential noise reduction to the extent of the noise mismatch. This is one reason I think bridge mode will sound better (it does to me on tentative first listening).
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The Purity Ultra GT is a tube unit with a claimed band width of 10Hz-35kHz -1dB. It doesn't appear to require a power supply that has a low dynamic impedance at RF frequencies.
The Lyra Connoisseur is a transistor based design that is out of production. I could find no information online about the circuit bandwidth. I like size of the power transformers. They must have felt that it sounded better with the polypropylene capacitor bank. I am a little more conservative in as much as my preamp and my phono preamp only have one 225 watt toroid a piece.
Thanks for being willing to satisfy my somewhat irrelevant curiosity about the DA on solid polymer electrolytics.
Scotty
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You're welcome sir.
I'm fairly sure these manufacturers are targeting primarily audio frequencies by their use of psu film capacitors. Fwiw, the c-j GAT is rated to 100KHz, the Ayre models to 250KHz.
I faintly recall reading Jonathan Carr regarding his opinion on electrolytics (doesn't like them). When I was fooling with fluorinert, Carr contacted me to obtain samples of capacitors I was designing for my personal use. So did Charles Hansen. Parts quality is evidently important to them.
In the Ncore, RFs are shunted to ground on the output. Audio frequency disturbances on the power rails pass nicely through into the speakers.
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As far as the Ayre VX-R and MX-R are concerned I can't figure out what all of those capacitors do in the circuit. Judging by the positive reviews however, something must have been done right.
My DM 220 amp's circuit boards don't have nearly as many caps, it's an interesting contrast in design philosophies.
(http://www.audiocircle.com/image.php?id=40162)
My gallery has a few more shots of the amp.
Scotty
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That's excellent. The fewer the capacitors the better.
I'm pretty sure (I think I recall reading) that the film caps in the Ayre supplies are largely electrolytic bypasses.
I'm not intending to suggest that using better capacitors solves the world's audio problems. I do think its an area of easy improvement. I mean, before Bateman actually measured capacitor distortion, who would have thought this about those tiny smd X7Rs:
(http://www.audiocircle.com/image.php?id=64924)
I hope Bruno's using COGs:
(http://www.audiocircle.com/image.php?id=64927)
They're almost as good as film/foil polypropylenes:
(http://www.audiocircle.com/image.php?id=64926)
Which are nearly as good as polystyrenes (Bateman's measures), which are almost as good as teflons, etc.
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It would have been neat if he had available to him the polymer tantalum SMDs to test.
In the photo of the amp you can see polystyrene bypass caps next to Panasonic FM caps which provide local storage for B+ and B- rails.
The bypassed BlackGate in the center of the board prevents the amp from having gain at DC and has been replaced by a Nichicon solid polymer AL electrolytic cap which does not benefit from a bypass.
Scotty
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Scotty, were polymer tantalums available to Bateman when he did his tests?
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Those articles were published in Wireless World in 2002. I don't really know when polymer tantalum capacitors became available. I would have thought, given the thoroughness of the the articles, that he might have tested them if they were available. However he was concerned with measuring the amount of distortion contributed by capacitors rather than conducting an overview of every type of capacitor available in the marketplace.
Both polymer tantalum caps and solid polymer electrolytic capacitors were not tested by Bateman.
In as much as these articles were written a decade ago neither type of capacitor may have been in production, but I couldn't say for sure either way.
Scotty
Here is a link to the Cyril Bateman articles in downloadable pdf form at the Pro Audio Design Forum
http://www.proaudiodesignforum.com/forum/php/viewtopic.php?f=6&t=153&start=2
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From a quick google search, the capacitors look new. Here's an article (pdf download):
http://www.google.ca/url?sa=t&rct=j&q=polymer%20tantalum&source=web&cd=9&ved=0CIABEBYwCA&url=http%3A%2F%2Fd0server1.fnal.gov%2Fusers%2Fbagby%2Fwww%2FL1_Cal%2FORC_Docs%2FFinal_Orc%2FADF_CAPS%2FKEMET_F3102PolTaPerChar.pdf&ei=Ghr_T8HaBJL9rAGE1KyMCQ&usg=AFQjCNHp1DhQolTIRURSbdLYW8w2Xgjhew&cad=rja
They look to have a very high DF ... <10% according to Mouser. That can't be right. Another data sheet puts their DF at a more reasonable 0.06 to 0.10% thereabouts.
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From the pdf doc "The inherent dielectric absorption of the solid tantalum capacitor .... typically equates to 1-2% of the voltage applied."
High but not 10%, what also has to be taken into consideration is the performance of the possible alternatives to a solid tantalum surface mount cap and how they might sound at a given position in the circuit. It makes sense to use the most appropriate part for the application in the circuit.
A ceramic might be a better choice depending on the what the cap has to do.
Scotty
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My friend with the first set of Ncores I made finally listened and then tried AMR fuses. He says the fuses made the amps fuller, cleaner and had more air. And this was using the amps on a two way bi-amped speaker on the bottom end. Basically running 20hz to 850hz......48db per octave xover. He loves the control and slam of the N-cores but feel his highly modified Hurricane amps have more air, texture and harmonics.
I will be firing up another pair of N-Cores in the next few days and I will try Furutech fuses and also bypassing the fuses with a piece of wire underneath the board to give a reference. Then I will be removing (ripping off) the .68uf output caps and dremeling off the sides of the caps and removing the steel leads and replacing them with OFC leads and marking the caps for outside foil. I will then replace the caps underneath the board (outside foil oriented to ground). I will also try removing one of the caps and see if it is still stable and if so will listen with 1.3uf instead of 2uf. If I like this effect, then I will replace the two .68 mylars with three modified Wima .33 polyprops.......lots to try. I will let everyone know what I hear and if the cap mod works great I will show pics of what I have done.
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Excellent, Ric. I think those mylar caps have to go and will be interested to hear what you find by replacing them as you intend.
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Btw, here is a quote from John Curl on the matter of bypassing, err, lousy capacitors (from his Blowtorch thread on DIY):
For Vendetta Research, I had to use a more sophisticated approach, in order to make it extremely low noise, and not contribute a sonic 'character' to the circuit. I found that ANY aluminum or tantalum cap that was used directly across the input circuit power supply would change the sound. Therefore, I had to find a quality film cap that would work OK.
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And another:
Once I heard differences in electrolytic caps in my Vendetta input circuit (thanks, Peter Morcrieff for showing this to me) over 20 years ago, I had to design them out. The 0.1 polystyrene cap on the output is not doing much at audio frequencies, and it sounds good as well, for some reason.
And here's a quote re power supply regulation:
The power supply is the biggest part of the active circuitry for the BLOWTORCH. It is composed of 3 passive stages, then 3 active stages of regulation and noise reduction, on each channel and each supply voltage, before reaching the actual gain stage that amplifies the music. The gain stage is about 2 square inches (rough estimate) for each channel. The rest is servos, and power supply.
And another:
I can hear the 'sound contribution' of the output electrolytic cap when it powered my folded cascode circuit. As an engineer, I would not have thought it possible, but I heard it in a direct AB test with a large value film cap, that sounded better. This forced me to use another approach ...
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And here is JC on DA:
'Smear' is a pretty good description of DA. I once used the term 'echo' for DA effects, more than 20 years ago in a LTE to 'Wireless World' or 'Hi Fi news'. I never heard the end of it from Doug Self, etc. , but 'echo' is a good first approximation. It is signal AFTER the original input has gone, and there should be only silence.
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JC is also an ardent bybee fan.....
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So am I. I once put one one the output of my OR5, and yes it created presumed reflections I could hear as jitter---so much so that my Tact would at times lose signal lock. I didn't like the jitter, but the sound was improved in desirable ways. The overall effect was almost a wash.
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Must have been the quantum gravity well disassociating the matter and anti-matter....
But seriously, with your ability to precisely hear and pinpoint all this minutia, you must have the most sensitive hearing of anyone I have ever heard of.....
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1/f noise is probably closer.
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It's in the fine details where major progress will be made to make these modules more pure:
1. All brands of surface mount resistors have a different sound (they all measure the same). Did Bruno A/B several brands to find out the one that is the most transparent? For instance, I tried a Dale surface mount resistor on the output of one of my clocks (100 ohm) and it sounded way worse than a Susumu resistor. Both are .1% thin film same size (0605) resistors....look identical. So, there might be major gains in replacing the resistors in the module.
2. The output filter caps are metalized mylar with steel leads. Also they are not oriented so the outside foil is toward ground. Better caps properly oriented here could make a major difference. Even larger more inductive parts here could make the sound much better. Is it better to have a super low inductance part that is non linear....or a higher inductive part that is more pure? I bet the purer part will give the better results. Obviously, you would not want the leads on these parts really long or the module might be unstable. Lots to play with here.
3. Bypass caps. All the amps that recently have been said to give better air, harmonics and slam versus the N-core I bet are using all film and electrolytic caps in the power supplies. Probably no ceramic caps in these other amps. Ceramic caps can sound very pinched sounding. The tiny surface mount ceramics are low inductance and fast but they still have the "ceramic" sound. There might be a couple of tiny ceramics on the input of the amps as well. Removing nome of these ceramics and changing to Teflon, styrene or modified Wima, etc. could open up the sound mucho.....and of course, just bypassing the power supplies with added Teflons as Serengetiplains is doing could also improve the sound. However, I bet the amp would sound better without so many ceramics on it.
4. The output coil: Looks like litz wire to me....this is very good. However, would a toroidal cored inductor sound better? When I was modding the first generation UCD modules I changed the output coils to toroids wound with litz wire. It certainly was better. However, I don't think the first generation modules had litz wire in the coils.
5. Electrolytic cap sound: I remember changing the main power supply electrolytics in the original UCD modules out for some Rubycon ZL?..... was way too bright and nasty, so I put the original caps back.....so these caps contribute to the sound of the amps. This is another thing to try.
I will be starting my work on the output filter caps and then work on the power supply bypasses. The resistors are a hard one as there is no schematic and it would be hard to figure out which resistors are the most important....not to mention the difficulty of soldering on such a tiny board.
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with all due respect to those with considerable modding skills, it might be very worthwhile to check out the links in Jason's post:
http://www.audiocircle.com/index.php?topic=108167.0
This is not to imply anything cannot be improved, but that many, many years of experimentation and development has gone into the little Ncore modules.
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Phil, I only monkey with gear I consider first rate.
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with all due respect to those with considerable modding skills, it might be very worthwhile to check out the links in Jason's post:
http://www.audiocircle.com/index.php?topic=108167.0
This is not to imply anything cannot be improved, but that many, many years of experimentation and development has gone into the little Ncore modules.
You are correct Phil Bruno discussed the issues surround the PCB layout and the effort that went into it controlling the emf and so on.
I would recommend that the 'modders' listen to the designer talk about the amp he designed.
Playing with the wiring going to and from the board, enclosure and so on is fine. tampering with the PCB is a no no if you want to keep the performance.
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splains,
no criticism meant, just that Bruno's talk, as Kevin points out, might provide useful information about tight tolerances and the like. It would seem that Bruno has tried and measured quite a few options and designs what does not meet the needed specs.
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It also might be fruitful to pay attention to his comments about power supply and ncore interaction......
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Phil, cab and kevin, I understand where you're coming from. Apart from adding some off-board bypass capacitors and regulated supplies, I personally don't plan on changing smd components or board layout, except perhaps to replace a few critical resistors with Vishay smds if possible. I'm unsure I can do so as the smallest Vishay smd is 0805. But in that event, maybe I can scratch some traces to fit these. We'll see.
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serengetiplains, I not sure you can answer this,but has the HF "lift" you heard due to the pwrs bypass caps subsided yet? I'm not sure if you have the bypass caps in place on the bridged Ncores or not. I was thinking that if the amps were left on 24/7, the hours on the bypass caps would quickly mount up and the breakin irregularities should be going away.
Scotty
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It did subside ... maybe 50%. The amps were sprawled on boards in my living room, so I dismantled them a few days ago. In the time they were operating, HF lift and stridency reduced as I thought they would, and due, I suspect, to capacitor break-in. Teflon capacitors to me typically sound awful when first used---edgy as hell despite immediately performing better in other regards. I typically have to prevent myself from judging their use a failure, and just be patient. Then after 100, 200, 300 hours ...
I was also using a cheap DAC which in headphone listening I found edgy (for me predominantly a HF phenomenon).
All that said, I liked what I heard. Given probable further improvements in capacitor operation and a better DAC, which will be an R2R topology, I think HF lift and edge will be sufficiently ameliorated to allow rather enjoyable listening. Btw, the amps sounded wonderful at low volume where HF stridency didn't so much irritate.
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I was also using cheap speaker wire, psu wiring was not ideal, etc.
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I see I have so much to learn from the experts who really know what matters: big caps and fancy materials, the sort of things that are simply over the head of the poor bloke who merely got the thing to work.
Still, from this humble position I would like to offer some interesting tidbits:
*the power rails are LC filtered. Not much PWM current gets out through the supply wires, it's mostly just the average (audio frequency) component. It's called "decoupling". As in "making sure circuits are no longer coupled".
*The electrolytic capacitor bank was designed to have a damped impulse response. Also, the series inductance of the capacitor bank as measured at the power stage works out as <1nH. The large film capacitors shown in this thread have an inductance that's fully determined by their size and attached wiring, and are probably more like 100nH. They won't be very effective bypass caps. That's putting it mildly. To get low inductance, get a small loop area which is not compatible with big components.
*DA (soaking) is irrelevant in DC applications. Besides, it isn't in any way improved by adding a small low DA cap across it...
*FET linearity is not dependent of heatsinking. FETs just aren't linear at all. Besides, Ncore is a class D amp... Not much sense in making FETs more linear then.
Give me some credit. There's still some wisdom left in this old brain.
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Ah and there I was thinking of painting my NC400's bright pink with the words SUPER TURBO written across them, would that harm the performance? I hope not I'm really REALLY keen on making them look SUPER COOL!
Please don't laugh but I have a theory that the color pink is the very best color "in the quantum universe" at suppressing RF and EMI emissions at the atomic and sub atomic level....discuss.
P.S If you would like to start using my pink paint on your Ncore's Bruno I have patent pending so I'm afraid it's going to cost you :wink:
ADVERTISMENT: Quantum Pink paint (patent still pending) with free SUPER TURBO sticker pack ONLY $299.99 per fluid ounce. I'm almost certain that it will improve anything beyond your wildest dreams. STRICTLY NO REFUNDS ACCEPTED
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I see I have so much to learn from the experts who really know what matters: big caps and fancy materials, the sort of things that are simply over the head of the poor bloke who merely got the thing to work.
Still, from this humble position I would like to offer some interesting tidbits:
*the power rails are LC filtered. Not much PWM current gets out through the supply wires, it's mostly just the average (audio frequency) component. It's called "decoupling". As in "making sure circuits are no longer coupled".
*The electrolytic capacitor bank was designed to have a damped impulse response. Also, the series inductance of the capacitor bank as measured at the power stage works out as <1nH. The large film capacitors shown in this thread have an inductance that's fully determined by their size and attached wiring, and are probably more like 100nH. They won't be very effective bypass caps. That's putting it mildly. To get low inductance, get a small loop area which is not compatible with big components.
*DA (soaking) is irrelevant in DC applications. Besides, it isn't in any way improved by adding a small low DA cap across it...
*FET linearity is not dependent of heatsinking. FETs just aren't linear at all. Besides, Ncore is a class D amp... Not much sense in making FETs more linear then.
Give me some credit. There's still some wisdom left in this old brain.
There you have it from the horse's mouth.....Thanks for taking the time to clear the air a bit....
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Bruno,
Unfortunately, even with the warnings that have been repeated over and over on diyaudio (http://www.diyaudio.com/forums/vendors-bazaar/190434-hypex-ncore-478.html), the modifiers continue to encroach upon your work with a very limited understanding of the ramifications of doing so. Moreover, they are willing to go against a young 39 old who has quite a few patents to his name especially within the field he is working in (unlike other high end audio pundits)!
All I can say is...thank you for doing what you do. We are nearly of the same age and I respect a man who not only provides his designs at such low cost to the diy community but also defends his product without pride nor prejudice, just pure facts.
Best,
Anand.
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Bruno,
Unfortunately, even with the warnings that have been repeated over and over on diyaudio (http://www.diyaudio.com/forums/vendors-bazaar/190434-hypex-ncore-478.html), the modifiers continue to encroach upon your work with a very limited understanding of the ramifications of doing so. Moreover, they are willing to go against a young 39 old who has quite a few patents to his name especially within the field he is working in (unlike other high end audio pundits)!
All I can say is...thank you for doing what you do. We are nearly of the same age and I respect a man who not only provides his designs at such low cost to the diy community but also defends his product without pride nor prejudice, just pure facts.
Best,
Anand.
+1 :thumb:
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Bruno, I'm sorry you feel disrespected. From what I see, you're a genius in electronics design, and on the very cutting edge of class D development, which I think is the cutting edge of audio advance. It looks to me that (and please bear with my language) digital is the future for audio generally, and class D, being a digital-friendly form of amplification, is the future of amplification. I really can't see it otherwise. Looking into the future, I sense that tubes and class A will remain as defined niches, but their advance, from what I can see, is now limited, as it has for some time, to component improvement---better amplifying devices, better passive components, but nothing fundamentally new on the horizon and therefore only incremental advance.
And yes, that post-modern levelling is finished. People are getting with that by moving into a systems awareness (the Libor collusion, among many other things, will put the last nail in the PM program). In audio, that means a complexity amenable to system-based understanding that incorporates all usable, successful discoveries of the previous class A and A/B era in a leap to something new at a more fundamental level.
So I really think you're on the cutting edge and respect your knowledge, ability and genius.
I am nowhere near a genius in electronics soldering let alone design. But I have other experiences I have come to trust and that have worked for me in my similarly dedicated 30 years of this pursuit. I'm just putting together some pieces here the most of which couldn't realistically be incorporated into a commercial design. There is, in any event of that, no need to imply that my or others' experience is simply valueless.
So far as large capacitors are concerned, my speculation is that these capacitors operate at audio frequencies. Lead inductance seems to me to ensure these capacitors will operate only such. I find using them to be an overall improvement. Among other reasons, there is only (from brief memory) 250uF? proximal to each channel's output. I have heard obvious effects of using film bypasses across much greater uF electrolytics. I also heard these effects on the Ncores. Speaker driver control improved and distortion decreased allowing me to listen at full volume while thinking I could turn the volume up considerably more. "That's all? Too bad."
I agree with you that DA is irrelevant to DC. But capacitors only operate on AC, and DA is relevant to any capacitor. And just like there is no digital amp (music is analogue), there is no pure DC. AC's everywhere.
In any event, thank you for your work and your brilliance.
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And forging at the cutting edge, you obviously have and will experience attacks from many angles. That's not what I'm doing here. I'm not, and I don't intend by implication to be so doing.
Looking at DA, which seems not fully or perhaps even poorly understood, if one uses the Cole-Cole method of calculation, wouldn't the effective frequency of DA release be much lower than the trigging signal to which a given release relates? If that's true, good capacitors operating at audio frequencies+ may be just the thing for a significant DA cleaning of the rails. J'speculate.
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Oh yes, and class D, to me, differs from class A and A/B by being what I like to call a dual technology. Not to start an endless semantics loop, but to make a point to say something I find interesting, class D is to me analogue and digital. It is digital insofar as it, for one part of its operation, renders the analogue signal a PWM pulse train. From Bruno's patent:
Pulse width modulation is a technique that can be used for converting an analogue signal into a binary signal ...
At that place of the binary codification of the analogue signal, one has latitude to, among other things, apply digital algorithms, so by definition a class D amp has access to a range of possible enhancements and solutions unavailable to the mono-technologies of classes A and A/B, C perhaps included, whatever the hell C is.
Dual thinking is quantum thinking: both. Both is always already a systems view that manifests, in audio, imho, as combining boths where they may lay: digital-analogue (detail-in-wave), electrical-magnetic (ditto), etc.
And quantum thinking/viewing/science is simply more powerful than classical-only push-pull energetics. No more post-modern levelling: more powerful is more powerful.
There's my 50000 foot view to supplement my DA and other ramblings. (both :) )
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Serengeti said it himself a few pages back: "I barely understand how this amp works".
That said, he is enjoying the hobby at a level I never will, nor will most here. He is a gentleman of the highest order, and is merely playing in his sandbox, enjoying himself. He is messing with them simply because he can.
It seems Bruno has changed the entire paradigm rather violently, in every way possible. I've made arrangements for a fully built pair and look forward to them, and they will be my second ever hifi amp.
But I recognized the achievement instantly: $2000 built, modules the size of a coaster delivering up to 1200 watts@4 ohms bridged with supreme alpha dog measurements, sipping a few watts at idle, beating and matching far more expensive amps. Beware Ncore and the eventual Ncore II, etc. Thing's done gone' and 'diffrent now.
The vast majority of the reviews so far are in high end systems and the owners positively laud this amp. People with decades of experience and owners of truly expensive gear.
I count myself a fan.
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Thank you, R. I think these amps must be practically unchallenged in what they do well. Really good stuff.
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@Serengetiplains don't worry I wasn't feeling you were disrespecting me. I was responding to several posts at once. It was someone else who irked me a bit by his style of delivery (can't remember the name). And indeed people should not feel stopped by theory to try out things. The important thing about theory is that it shows what is known, what is likely and what is unlikely. Once you find something completely unexpected by experiment you can try questioning theoretical assumptions. That's what experiments are for.
Usually they're not so much fundamental things but merely overlooked consequences of established theory. So far I found most audio "mysteries" to be mysterious only when theory is oversimplified. For instance, people who expect wiring to be of no importance will stay baffled until they stop confusing actual theory with simplifying assumptions. The converse doesn't help either of course, people who latch on to the first "explanation" they find and who then attach their whole world view on that (the wire metallurgy brigade springs to mind).
So when you say you expect adding caps to do something at audio frequencies, I cannot rule that out. What theory does say is that the soaking hypothesis (not sure who brought that up) would be an unlikely explanation for any audible changes. Some of the anecdotal reports suggest that many caps add the same character whether used as coupling or as decoupling. What that indicates is that soaking might not be the principal source of "cap sound". Whenever I hear soaking touted as "the answer" I go "think, boys, think"...
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It was I who raised the issue of capacitor soakage (Pease's term). Whether soakage or DA accounts for the principal source of capacitor distortion is I think open to question, but what can be said is capacitor dielectric effects---a more general umbrella term for capacitor distortion differences---show up consistently for different dielectrics in test results, showing characteristic distortion spectra for the various dielectrics in question.
As to series/shunt uses of capacitors, Bateman measured distortion differences between series vs. shunt uses and found those differences to be minimal. An example of this is shown below, with two diagrams also appended to show the test setup he used. In that setup, Bateman simply switched the position of the series resistor and DUT to change the position of the DUT from series to shunt.
(http://www.audiocircle.com/image.php?id=65276)
(http://www.audiocircle.com/image.php?id=65277)
(http://www.audiocircle.com/image.php?id=65278)
(http://www.audiocircle.com/image.php?id=65279)
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Notice that Bateman specifies film/foil polystyrene capacitors as the coupling caps in his test setup. He found that the resolution of his measurement instrument was limited by the distortion (resolution) of these capacitors. That makes sense. One cannot measure something that is beyond the measurement capabilities of the machine in question. Analogously, one cannot photograph anything smaller than the highest usable frequency of the light used in the photographic setup. Quantum physicists know this problem intimately.
Here is a quote from Bateman discussing this issue, followed by his ruminations on parts quality:
I started by carrying out some initial capacitor intermodulation tests. Experiments involving simple harmonic distortion testing revealed easily interpreted differences when testing less good capacitors. Testing good capacitors however confirmed that my existing signal generators introduced far too much distortion.
(http://www.audiocircle.com/image.php?id=65280)
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@Serengetiplains don't worry I wasn't feeling you were disrespecting me. I was responding to several posts at once. It was someone else who irked me a bit by his style of delivery (can't remember the name). And indeed people should not feel stopped by theory to try out things.
bruno, serengetiplains - what a treat to find such cordiality in a discussion on such a contentious topic. I last saw the like almost a decade ago.
Thank you both.
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Tip of the hat to you, gnomon.
I was trying to imagine how DA might manifest in a simplified circumstance. By DA, I mean capacitor distortion attributable solely to the workings of the dielectric in question. Other forms of capacitor distortion or non-linearity---ESL, ESR, DF, microphonics, etc---of course manifest without rest, but here I want to focus on this matter of charge retention.
DA measures the rate at which a capacitor regains its charge after having been discharged. That charge recovery is to my thinking a quasi-active source of spurious voltage that adds to or subtracts from the capacitor's output voltage---whether a signal voltage in the case of signal transmission, or DC stability in the case of output power rails. The capacitor output will modulate at frequencies of the dielectric's characteristic voltage recovery as that voltage appears progressively on the capacitor's output. From what I can discern, DA voltage frequencies, as it were, are much lower than the original voltage charge to which that recovering DA voltage refers.
Here's something I find interesting. DA is usually described as a charge recovery. I suspect that the mechanism responsible for charge recovery---a kind of dielectric response-sluggishness---operates in both the charging and discharging process. If this is true, it implies that a capacitor having a given DA will not only discharge spurious voltages after a charge, it will also not receive the charge's instantaneous value. I think the latter implies that charge peaks are to the extent of dielectric sluggishness clipped. The dielectric simply hasn't the quantum-molecular speed to absorb the full charge before that charge changes---the more for a fast-moving transient. High DA capacitors have always sounded dull to me, electrolytics being the worst given their reigning status as the highest DA capacitor type. I think dielectric sluggishness, working in both the charge-receiving and -discharging functions of the capacitor, accounts for at least part of this. Slow in and muddied out, and where did the subtle information go?
I look to more than listening impressions and theoretical implication to substantiate this idea of charge-receiving sluggishness. I performed tests on capacitors where I charged them for increasing times and measured the recovery voltage. In this test, I charged a 3.3uF PIO capacitor for successively longer periods of time, increasing the total charging time by 5 minutes for each next charge. Interestingly, the DA recovery voltage hit its highest level at 70 (!) minutes. This, to me, implies that the capacitor only slowly receives (imprints with?) the uppermost level of the original charge. A 70 minute transient is not what I'd call a transient.
In looking at how I conducted the experiment, I could have given greater time between successive charging cycles, but DA recovery to peak recovery voltage was fairly quick, and that recovery voltage then subsided just as quickly (at most, tens of seconds).
Also, on the numbers, peak recovery voltage represented almost 2% of the original charging voltage. This number should be increased given voltage leakage of my measurement setup.
Here are the results:
(http://www.audiocircle.com/image.php?id=65302)
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I was looking at the data of DA tests I performed. From this data, I noticed two variables in respect of DA recovery voltage. The first was the peak recovery voltage attained. The second was the time it took for that peak to be reached. Looking at the data through squinted eyes, I see the following patterns:
1) peak recovery voltage is higher the higher the capacitance
2) peak recovery voltage is higher the lower the DCV rating of the capacitor
3) peak recovery voltage is lower the lower the dielectric constant
4) time of peak is higher the higher the capacitance
5) time of peak is higher the higher the dielectric constant
All other things being equal, then, the lower the dielectric constant, the higher the dielectric DCV rating and the lower the capacitance, the lower the peak recovery voltage and the time peak is reached.
1) shows that DA recovery voltage magnitude relates directly to the capacitance of the capacitor. This implies that DA recovery voltage is based on area, as greater capacitance means greater area. Greater capacitance also means greater volume of dielectric being acted upon. But area seems the true measure. Bateman explains that DA recovery voltage is greater the greater the stress placed on the dielectric as measured in volts per micron of dielectric thickness. Volts per micron decreases when dielectric thickness increases. I found this in 2) above.
DA recovery voltage therefore looks to be a product of the k of the dielectric, the area of dielectric involved and the dielectric thickness, something like:
(k x area)/thickness
Time of peak seems likewise a product of the above equation. Though I don't have enough data to see a reliable pattern with the thickness element of the equation, dielectric thickness seems inversely correlated with time of peak. Time of peak otherwise correlates with k and area.
One outlier in the data concerned capacitors with combined liquid/solid dielectrics. Typical oil capacitors tend to display large peak recovery voltage but a comparable time of peak comparable to other dry capacitors of the same capacitance. Thus a Jensen 3.3uF PIO capacitor had a recovery voltage (~485mV) 750 times that of an RTX 3uF polystyrene (0.646mV), but the two reached that peak in approximately the same time (55 seconds for the Jensen, 45 seconds for the RTX styrene).
The oil used in oil capacitors, not to mention the paper, typically has quite a high k (4-8 depending on the paper or oil used). The increased DA recovery voltage for high k dielectrics shows in my data.
The worst type of capacitor is a large electrolytic. I tested an expensive Black Gate 1,000uF non-polar FK 50V capacitor. It's recovery voltage was about 3X that of the Jensen, but its recovery time was 60X that of the Jensen.
Bateman speaks to the better distortion performance of non-polar electrolytics over that of polarized types. A 100uF WKZ 500V Black Gate gave a peak recovery voltage 5X that of the 1,000uF FK (time of peak was not recorded).
It seems to me that both the absolute peak of recovery voltage attained and the time it is attained affect a capacitor's audible performance. The best capacitors, to my ear, perform best in both respects: they demonstrated both lower peak V and lower recovery time.
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I think the above gives a decent view of DA. My own experiments, limited as they were, follow results predicted for DA (Cole & Cole) and largely conform to experiments Bateman and others performed to test DA across differing dielectric types. Generally speaking, DA is worse the larger the capacitor and the higher dielectric constant.
How might this understanding apply to the Ncore? Here's my hunch. The Ncore draws a series of pulses from the power supply. Those pulses induce, among other disturbances, pulse-like voltage variations on the supply's complex dynamic impedance. The current pulses are for their part square wave composites of the amplified analogue waveform + switching harmonics. The psu voltage variations they induce will be a distorted version of those pulses. It is these variations, among others (like mains noise etc), that the electrolytic capacitors are placed to filter. Anything not filtered passes directly into the speaker. Because psu variations follow the music signal to some degree, and in other ways bounce around in some complex fashion (= a fashion that, imo, is sufficiently high to escape characterization, therefore not random), their presence in the audio band will muddy and distort the reproduction, quite audibly so.
I know the Ncore's feedback, in its limited way, addresses part of the distortion generated by these supply variations; so, too, does differential cancellation (PSRR). Because these are limited remedies, and because feedback introduces problems like higher-order distortion, the more one can eliminate noise from the rails before feedback and differential cancellation the better. I follow the rule that any node in a circuit is in its most general sense a voltage divider. The less noise appearing at any given node, the less is passed through to whatever next stage (or speaker) that node feeds.
All other things being equal, it seems to me that audio-band supply noise is perhaps the worst for class D amps. In addition to the normal range of supply disturbances affecting audible frequencies, class D amps also have the following:
• Switching noise modulating audio and audio+ frequencies. I maintain that frequencies beyond 20KHz are audible in some form of sensory perception. I can personally hear these frequencies as something of a pressure affecting my hearing, particularly where those frequencies are incoherent with the musical signal. I hear this effect with SACD and PWM amplifiers, and I suspect the use of feedback complicates the type of noise present (reference Pass' article on feedback-related IM effects).
• DA noise. My tentative theory concerning DA noise in class D amps is this: because DA recovery voltages are fractions of the original inciting frequency---the UHF pulses---this noise looks undoubtedly to reach downward into the audible (including audio+) frequencies.
It seems to me that part of what I hear wrong with class D HFs---their opacity, lack of sparkle and fineness, etc---traces to the above sources of noise, which are largely unique to class D design. The level of this noise looks to me to trouble just those HF subtleties I find missing in class D, including Ncore, reproduction.
And fwiw, and apart from DA, Ncore output capacitance looks to me insufficient to filter any such audio-frequency voltage variations. At 100Hz, 250uF has a capacitive reactance of about 6.4 ohms. Depending on the speaker's impedance, noise appearing at or near that frequency will virtually halve between the capacitors and the speaker. I'm uncertain what capacitance the Hypex smps has after its output, but from memory it seems that most of that capacitance resides one stage back in that supply.
______________________________
There's my long answer---the many posts above, including this one---to why I prefer to bypass output capacitors in this amp.
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I'm glad you did not bring up tensor theory on curvilinear coordinates on the above... :lol:
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You might find a more receptive audience for your thesis on diyaudio.com
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Shall I take a poll?
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Maybe I should have said "informed" instead of receptive.....
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Another insult.
What I'm doing here is groping for a rationale for something I hear and have often heard, and in a way I personally find technically plausible. If you have technical objections, I'm open to hearing them. Even Bruno said he can't rule out those caps doing something at audio frequencies. Because DA is a lower-frequency distortion (lower than the original voltage charge that incited the DA response), bypassing DA-rich electrolytics would seem a likely candidate for improving performance in that respect.
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Not an insult at all....It would simply seem that the technical nature of your posts above would find a more relevant audience on a more technically oriented forum.
So you are trying to lower distortion? At what level is it below the audible threshold?
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So you are trying to lower distortion? At what level is it below the audible threshold?
Yes.
For sure at zero distortion.
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If you don't know at what level you can hear distortion, how do you know if a lowering of distortion is audible? How can you be certain that what you hear isn't simply a more preferred distortion?
Since the distortion of the stock ncore is undoubtedly already lower than everything else in your playback chain, wouldn't it be a more plausible pursuit to try and lower the distortion in the components that have distortion that is factors greater than in the ncore?
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+1
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You might ask when distortion measurement is at the limit of what in the audible world it can measure. That's the real question, isn't it? How else can one explain the improvement of our measuring abilities? On that note, I think Bruno thinks his next amp will be better. I'm interested in the question of how that is possible.
I'm one of those guys who doesn't buy that measurements explain more than just a part of what is audibly relevant. And as far as they go, the measurements are good. We fundamentally want an amplifier with zero distortion. Measurements give us an insight into what we then in the language of those measurements can describe as an audibly relevant factor. But there is much more going on in the audio field---I'll call it a field, comprised of inner and outer processes---than measurements can measure.
Let me get a little subtle here. Measurements are a means of particularizing. They say and point to this. But what they miss in particularizing---particular being limited, by definition---what they miss in defining and limiting is the relation between the thus-called defined, limited parts (measurements). And because music is one wave, that relation is a relation as of a whole. Only ever one wave---unity, whole. Measurements only ever approximate in the direction of the whole, which is why things improve.
Put it this way. We have, among many others, THD measurements and IMD measurements. What measurement gives us how those two relate? Do you see the problem there? If you have the measurement that tells you how those two relate, you have a more powerful measurement than either THD or IMD, in which case you'll be using neither in favour of the more powerful measurement. Quantum physicists don't resort to Newtonian equations to do what quantum physicists do as quantum physics. And nuclear be much more powerful than grind-and-bump force.
People get a feel for music, that it's off in this or that way. What is that feeling? It must be an intuited sense of a difference between real and not. We listen to real sounds all day every day. We know what real is. But because it's real, we can't define it---there's nothing to which to compare it! And by extension, it thus is impossible to precisely characterize how something is not real. Why? Because the comparator can't be said. Measurements truly are limited.
Gödel in a nutshell.
(http://www.audiocircle.com/image.php?id=65643)
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Paul McGowan wrote similar comments today in his daily letter.
http://www.pstracks.com/pauls-posts/close-perfection/7526/
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Indeed, my stereo doesn't sound like real sound in all those ways it doesn't. We improve (compare 24/192 to that heard by the master's cringing dog) by trying something new, and the new can only be measured when implemented. But where does the new come from? It comes from intuition. Bruno tried something new, and yes, what he implemented lowers distortion, but he had to grok some assumption somewhere that allowed seeing more deeply into processes to allow advance to occur. Measurement, per Gödel, is always but an aid to perceiving more deeply into fixed assumptions that need to be overturned. The best way to forestall that process is to assume there's nothing new under the sun ...
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Do that google thang on 'Timothy C. Neugebauer inductance cancellation'
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Ha ha. Gödel, what a treasure he left us. All our sets (our theories, our measurement regimes, our mathematizations) exist as a box. Each axiom in a set refers to, gains meaning from, assumptions on which it is based, which implies this: to create a larger, more capable set (or understanding etc), one has to question assumptions, which are tacit, invisible, the water in which one swims. In other words, any advance arises from thinking creatively, outside the box.
Thanks for the Neugebauer link. I had a similar idea a few years ago to this in one of N's papers, and wondered how the compensation winding could be used in an active voltage regulator:
(http://www.audiocircle.com/image.php?id=65665)
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You might ask when distortion measurement is at the limit of what in the audible world it can measure. That's the real question, isn't it? How else can one explain the improvement of our measuring abilities? On that note, I think Bruno thinks his next amp will be better. I'm interested in the question of how that is possible.
I'm one of those guys who doesn't buy that measurements explain more than just a part of what is audibly relevant. And as far as they go, the measurements are good. We fundamentally want an amplifier with zero distortion. Measurements give us an insight into what we then in the language of those measurements can describe as an audibly relevant factor. But there is much more going on in the audio field---I'll call it a field, comprised of inner and outer processes---than measurements can measure.
Let me get a little subtle here. Measurements are a means of particularizing. They say and point to this. But what they miss in particularizing---particular being limited, by definition---what they miss in defining and limiting is the relation between the thus-called defined, limited parts (measurements). And because music is one wave, that relation is a relation as of a whole. Only ever one wave---unity, whole. Measurements only ever approximate in the direction of the whole, which is why things improve.
Put it this way. We have, among many others, THD measurements and IMD measurements. What measurement gives us how those two relate? Do you see the problem there? If you have the measurement that tells you how those two relate, you have a more powerful measurement than either THD or IMD, in which case you'll be using neither in favour of the more powerful measurement. Quantum physicists don't resort to Newtonian equations to do what quantum physicists do as quantum physics. And nuclear be much more powerful than grind-and-bump force.
People get a feel for music, that it's off in this or that way. What is that feeling? It must be an intuited sense of a difference between real and not. We listen to real sounds all day every day. We know what real is. But because it's real, we can't define it---there's nothing to which to compare it! And by extension, it thus is impossible to precisely characterize how something is not real. Why? Because the comparator can't be said. Measurements truly are limited.
Gödel in a nutshell.
(http://www.audiocircle.com/image.php?id=65643)
Nice but if you can't or don't measure something you have no way to know if it is really an improvement or simply a difference.
And none of this addresses the issue of the weak(er) links in the chain. Why spend the time on the strongest link? That makes no sense......
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And none of this addresses the issue of the weak(er) links in the chain. Why spend the time on the strongest link? That makes no sense......
Will hearing aids improve our reception/perception?
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I am afraid that improving the weakest link (the recording) in our systems is completely out of our hands. The recording engineers still believes that Monster Cable is state-of-the-art.
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That's my view also, Tom. And up the chain from there, the next most-important link is the digital signal whose distortions are amplified by the rest of the chain.
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Here's a picture of the innards of the Octave preamp. Notice the cascade of film capacitors bypassing power-supply capacitors in the psu on the left and in what looks to be the power supply section in the main chassis (upper left).
(http://www.audiocircle.com/image.php?id=66013)
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And here's the Soulution 720 preamp. Notice the film bypasses.
(http://www.audiocircle.com/image.php?id=66606)
(http://www.audiocircle.com/image.php?id=66607)
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Question: why not use cheaper electrolytic bypasses? Less inductance with electrolytics, yes?
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I want to hear NC1200 and/or bridged NC400 because of my personal experience with NC400MB (mono blocks). Speakers are my Ambiance/Mode Cancelling array, two stand mount monitors per channel (each monitor 5.3 Ohm minimum), wired either parallel (2.65 Ohm minimum) or series (10.6 Ohm minimum). A thread in the Speaker "Enclosure" circle has diagram and description. True sensitivity is 88 dB/2.83V/1M, 3000cf room, three channel Trinaural System, mains active crossed 2nd order @ 80 Hz.
NC400MB sound quality is so much better (in every parameter) driving the latter load that I have no interest in hearing it drive the former load. This is a surprise and disappointment because the first reason to build mono blocks was 4x higher voltage potential driving the former load (the second reason was shortest possible speaker cables).
Driving 10.6 Ohm minimum load impedance, I presume NC400 maximum voltage swing is identical whether an SMPS600 drives one or two NC400. To what extent do readers agree/disagree? If correct, then the only purpose served by one of my SMPS600 is 6' shorter speaker cables.
In this room maximum SPL is just below live. Hence my desire to hear NC1200 and/or bridged NC400. Other than that, I'm a happy camper and never heard any amp I like better.
It seems critical to confirm the speaker's minimum load impedance before judging NC400 performance. If NC400 luminescence and tonal density falls short of your favorite tubes, insure you audition a speaker with minimum impedance magnitude close to 6 Ohms before making a final judgement.
At that point, you can decide if NC400 performance justifies different speakers or if NC1200 or bridged NC400 are the best compromise.
Which OEM plan live NC1200 demo @ CES?
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It is interesting that you should find the performance difference so great between the two speaker loads; one of the main design goals and performance targets as expressed many times by Bruno is the load independent response of the ncore. Looking at the frequency response at different loads confirms this. It might be beneficial to ask Hypex about this.....
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It is interesting that you should find the performance difference so great between the two speaker loads; one of the main design goals and performance targets as expressed many times by Bruno is the load independent response of the ncore.
I agree entirely, hence my "surprise and disappointment." The lower sound quality (higher and/or more distasteful distortion content) commensurate with the lower impedance prevents me from enjoying 4x larger voltage envelope.
Looking at the frequency response at different loads confirms this. It might be beneficial to ask Hypex about this.....
What about distortion content 2.65 Ohms vs. 10.6 Ohms?
I think I will contact Jan-Peter or Bruno, but only after I confirm the actual minimum load impedance, which might possibly (though doubtful) be less than 5.3 Ohms @ 200 Hz (flat 4 Ohms above 600 Hz) per monitor (2.65 Ohms with two monitors in parallel). There's no known reason to disbelieve the OEM impedance graph by the original speaker designer.
Till then, an appropriate question to Hypex might be:
With levels matched (series +6dB, parallel -6dB), within NC400 maximum current and voltage envelope, how do you quantify expected maximum quality difference between the two loads described above (identical except for minimum impedance)?
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From what Bruno has said, there should be no difference in performance from 2 ohm past 8 ohm, and I would suspect much higher than that. Your experience clearly is at odds with both the published performance and Bruno's statements regarding the load independent performance. I would definitely talk with them....
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It must be said though that, high as the damping factor is, it will still double into double the load resistance, so quadruple from 2 to 8 ohms - and perhaps this is audible.
Another thought is that perhaps the speaker wire should be doubled up or the gauge increased as the load resistance lowers, to remove another variable. The wire almost certainly will have more resistance than the output stage as Bruno says in the white paper:
"Output impedance is lower than the resistance of three feet of 4 gauge loudspeaker cable."
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It must be said though that, high as the damping factor is, it will still double into double the load resistance, so quadruple from 2 to 8 ohms - and perhaps this is audible.
Another thought is that perhaps the speaker wire should be doubled up or the gauge increased as the load resistance lowers, to remove another variable. The wire almost certainly will have more resistance than the output stage as Bruno says in the white paper:
"Output impedance is lower than the resistance of three feet of 4 gauge loudspeaker cable."
Russell,
Huge thanks for the speaker wire gauge info above. You may have just quadrupled my amp's power.
My speaker wire is Stan Warren's original recipe, Quad-braid AWG12 (19-strand copper per each conductor, 2x AWG12 per polarity), about 6' total whether series or parallel. IIRC each doubling of gauge = next thicker gauge/next lower whole gauge number: two x AWG12 = AWG11. If correct my equivalent AWG is only 11.
By Bruno's math, driving 2.65 Ohm load, how many times must I multiply/parallel 6' wire equivalent to two x AWG12 per polarity (4x AWG12 both polarities)?
Again, the sound quality difference was huge, swinging from unacceptable/how much can I get for these amps? to equaling or beating the best I've heard.
I certainly thought, apparently wrongly, my wire gauge was way over-spec even for parallel application. dB loss per this wire gauge calculator http://www.bcae1.com/images/swfs/speakerwireselectorassistant.swf (http://www.bcae1.com/images/swfs/speakerwireselectorassistant.swf) calls for thicker wire gauge if/when loss exceeds 1 dB, while AWG11 results in only .05 dB loss (1/20th allowable) listing 600W amp power @ 2.65 Ohms @ 6' wire. Quite confused!
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IIRC each doubling of gauge = next thicker gauge/next lower whole gauge number: two x AWG12 = AWG11. If correct my equivalent AWG is only 11.
Doubling conductors results in an ~ equivalent gauge 3 sizes larger. 2 X 12AWG = 9AWG. If you are combining an odd number of conductors, or conductors of different sizes, you can use an online wire gauge calculator such as:
http://home.hiwaay.net/~rgs/awgcalculator.html (http://home.hiwaay.net/~rgs/awgcalculator.html)
Steve
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We have 3 people who have the NC1200s and have compared them to the NC400s. They all say they are better.......but nobody is saying more than that. In what exact ways are they better? Can you give some details?
I wonder how a pair of NC1200s will compare to bridged NC400s (bridged 400s are $3500 and NC1200s are $9000).....assuming both being run the same way (either balanced or unbalanced). I am talking sound quality.....not power. I only need 10 or so watts.
By the way, just listened to NC400s (hardwired AC, hardwired output wires, OFC unbalanced input jack, Furutech fuse and 10lbs of damped weight on top of each of them). These things are very nice......slight loss of air on top and not as directly involving in the midrange as my own amps but they are more detailed and lower distortion. If you could marry the characteristics of the two amps I would be in total goosebump heaven. For this reason I am interested in the bridged amps and also doing some minor mods to the module (modifying and possibly changing the output filter caps). The Furutech fuses made the amp more palpable and rich....very nice.
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Well bridged NC400's are more powerful than nc1200, correct?
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...The wire almost certainly will have more resistance than the output stage as Bruno says in the white paper:
"Output impedance is lower than the resistance of three feet of 4 gauge loudspeaker cable."
Per calculator link I posted above: 3' x AWG4 = .0015 Ohms, low for any power amplifier.
Earlier calculator specs testing the monitors in parallel:
600Wrms
6'
AWG9
2.65 Ohm load = .0095 Ohms wire resistance (6.3x the source).
I'll listen again with AWG6 x 3.5' = .0028 Ohms (still twice the source but 3.3x lower than the earlier test).
Depending on the speaker's minimum impedance and speaker cable gauge, you might consider revisiting negative Ncore conclusions.
If Hypex sells speaker cable, what is the gauge?
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No Guy, no need. I was being obtuse. My bad. I agree that these NCore threads are getting a little snippy, and my poor excuse for an inside joke didn't help.
OMG Ted! The last time I heard the word obtuse was in The Shawshank Redemption(one of my alltime favorites...). :lol:
Sorry...back to the thread...
Randy
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I only need 10 or so watts.
By the way, just listened to NC400s (hardwired AC, hardwired output wires, OFC unbalanced input jack, Furutech fuse and 10lbs of damped weight on top of each of them)...
"Unbalanced input" is contrary to OFC and every assembly technique above. Per Bruno: ideal input is balanced XLR regardless whether source is balanced or unbalanced. Unbalanced input also negates function of Bruno's ideal unbalanced source IC, which is quasi-balanced. A strange and cross-purpose assembly philosophy. One should at least follow the designer's direct ideal instructions before "improving" other areas.
I bet this was the owner's logic: he has unbalanced source, some preferred unbalanced IC, some favorite OFC RCA jacks valued about $75ea, and desired not to make or purchase new quasi-balanced IC.
I don't know if it's true, but IIRC decades ago Enid Lumley wrote that when "RCA Labs" (it's almost impossible to believe that Dr. Harry F. Olson worked for RCA when he wrote "Music, Physics, and Engineering) invented the then-labeled "phono" (AKA RCA) connectors, RCA had no specific ID for the diameter of the signal tunnel, hence the wide range of tensions in the plug/jack interface.
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OFC means oxygen free copper.....don't know what you think it means. Almost everyone who listened to the amps on tour unbalanced used the supplied adapters. This simply grounds pin three to pin one......the same as using an RCA jack.....no difference whatsoever. A great sounding rca jack will sound way way better than using an adapter. The only possible? advantage of using an XLR would be to use a floating quasi-balanced interconnect which probably very few have done (you need to have an rca on the input side of the cable and an xlr on the output side). Two of the three "unbalanced" inputs that Bruno shows on the NC400 data sheet use RCA jacks.
The REAL advantage comes when you fully balance, which I will be hearing soon (fully balanced Oppo going directly into fully balanced NC400).
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does the oppo have a digital volume control?
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OFC means oxygen free copper.....don't know what you think it means.
I know and knew what is OFC. My point was and is that if absolute performance is the goal (tweaks, etc), XLR/quasi-balanced IC performs better than OFC RCA/unbalanced IC. Maybe you disagree and that's fine.
You ignore my point that Bruno's ideal for unbalanced source is XLR with quasi-balanced IC. Your silence says much. I don't blame you for ignoring it, because I suppose ignoring Bruno's advice in this regard is hard to defend.
Would you be so kind as to share with readers the builder's logic in choosing RCA jack/unbalanced IC rather than XLR/quasi-balanced IC. We may all learn something from this choice. I suspect the builder thinks he has some special RCA/unbalanced IC that negates Bruno's first choice.
Almost everyone who listened to the amps on tour unbalanced used the supplied adapters. This simply grounds pin three to pin one......the same as using an RCA jack.....no difference whatsoever. A great sounding rca jack will sound way way better than using an adapter. The only possible? advantage of using an XLR would be to use a floating quasi-balanced interconnect which probably very few have done (you need to have an rca on the input side of the cable and an xlr on the output side).
I wonder what on earth the above has to do with anything relative to my comments about the mutually exclusive assembly philosophy employed by the builder of the amp you describe: hard wired inputs/outputs, etc. while simultaneously employing inferior input jack and IC architecture. May I ask who made these choices?
Two of the three "unbalanced" inputs that Bruno shows on the NC400 data sheet use RCA jacks.
What you mention above Bruno labels as only "acceptable". About the preferred method I describe Bruno writes: ""The braided cable shield serves two duties: to connect the chassis potentials together and to shield electrostatically the signal". I can only presume the RCA deletes these features.
The REAL advantage comes when you fully balance, which I will be hearing soon (fully balanced Oppo going directly into fully balanced NC400).
About which you label (unheard I might add) "REAL advantage" Bruno says the XLR/quasi-balanced IC "benefits unbalanced setups almost equally". I'm confused by "fully balanced NC400" because by design NC400 has fully balanced input. Only the DIY builder, such as in the subject amp, decides to convert a fully balanced input into unbalanced with inferior RCA jack vs. XLR/quasi-balanced IC, contrary to the designer's first performance choice. Please correct if I'm wrong.
Thanks.
About your amp's architecture Bruno further writes:
Having made sufficiently clear that there is, in fact no reason why anyone should ever want to waste a perfectly good balanced input by putting the module in a box with RCA inputs, it is likely that some will persist. (emphasis added)
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(http://www.audiocircle.com/image.php?id=67667)
(http://www.audiocircle.com/image.php?id=67666)
The images are not the way I listened. This is for the customer. I ran the power wires backwords and over the front of the amp and soldered them to my powercords. I used the speaker output wires but hardwired directly to my speaker wires. The binding posts shown are used as clamps only. I invented this technique and have been using it for over 10 years. Even better sounding is to use a plastic or wooden clamping mechanism. This is especially important at the speaker end of the wire where all the conductive mass of a connector acts as a bad "ground or hot enhancer".....more like a ground or hot ruiner. So, at the speaker end it is seriously important to hardwire or at least have no massive metal posts.....even as clamps. The speakers I am designing will have plastic or wooden (optional) clamping mechanisms. The AC connector for the customer is a Furutech and you can see the blue Furutech fuse in there. I will be modding or changing the three Wima output filter caps soon.
Jim,
Have you listened both ways?......please tell us how much better it sounds to use an xlr on the amp and reterminate your unbalanced cable with an xlr. The only thing that makes a sonic difference/improvement is what makes a difference.....not some thought about it.
The only difference between "quasi balanced" and unbalanced is the fact the the negative input of the differential pair is grounded back at the source (one meter away) and not at the load. How much difference sonically does this make? Please enlighten us as to the sonic benefits.
As far as tweaks go, it does not matter which way you hook up the inputs.....you will still hear all the benefits of hardwiring, etc. believe it or not. The same as not using a lower distortion fuse. Even with the stock fuse (almost everyone who has the amps still has the distorted fuse sound) you can still hear anything else you do to the amps. You do not have to do one thing in order to hear another. However, the more veils you remove the easier it is to hear differences and the more pronounced they are.
It has been clearly said by several people that the best sound comes from running the amps fully balanced. Quasi-balanced is not balanced at all. Balanced means you have both a positive and negative going signal (relative to ground).....and fully floating differential stage.
Now we have someone raving about balanced bridged.......this is getting exciting. If balancing gets me more (I will soon find out) and then bridging gets even more then we are all in for a big treat.
Yes, the Oppo has a 32 bit digital volume control.....however, I bet it is not sonically as good as using a shunt attenuator directly inside the amp (what I do). A couple of my customers say the digital volume control still messes up the sound. I have not played with it personally. Putting a shunt balanced attenuator in an amp would be pretty easy. You could use a 10K resistor in series with each input and use a 24 position switch to switch resistors between the output of the 10K resistors. Very transparent. PRP resistors are very good for the money. Only slighty better is nude latest Vishay.
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Ric any chance we can gets some pics of inside the amp?
thanks, mike
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The only difference between "quasi balanced" and unbalanced is the fact the the negative input of the differential pair is grounded back at the source (one meter away) and not at the load. How much difference sonically does this make? Please enlighten us as to the sonic benefits.
The signal itself does not need to be differential to benefit from the balanced design of the amp: any noise picked up by the balanced cable (in the quasi balanced approach the negative it is indeed grounded back at the source) between the source and the amp (noted noise hereafter) will be eliminated by the balanced design of the amp because is subtracts both signals:
cable 1: positive signal+ noise
cable 2: zero negative signal+ noise
in the amp: cable1 minus cable2 signal provides a cleaner positive signal.
In the fully balanced setup it would be
cable 1: positive signal+ noise
cable 2: negative signal+ noise
and cable1 minus cable2 would provide a signal doubled without the noise, hence evenmore improving signal/noise ratio
Hope it makes sense .
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Someone needs to do a listening experiment to confirm if there is any benefit from "quasi balanced". The most simple way would be to have a balanced connector on the amp and a balanced connector on the amp end of the interconnect. One way you would ground the negative input of the differential stage directly inside the amp at the jack and the other way you would have it floating at the amp so it is only grounded at the source. Listen for the difference and let us know. Otherwise it is all theory.
The only thing real is what you hear. Your senses tell you what is real.....not a scope or measurement tool. The NC1200 measures worse but sounds better. Why is that? There are many, many reasons why things sound different and most of the time we cannot measure what we hear. A better fuse will not make the amp measure better, nor better wire, nor eliminating the jacks, nor damping nor adding an Audiomagic Pulse Gen ZX....on and on, but the ear ears the improvement. I am totally for great engineering....and the NC400/1200 are that and more. However, great tweaking is just as important......this has been my finding from experiments and listening tests starting in the mid 70s.
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Ric were can I get either plastic or wood speaker wire clamps.
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US Plastics has very cheap one quarter inch x 20 nylon threaded rod, washers and wing nuts. You can cut the threaded rod to the length you want and epoxy it into your custom speakers. Then use a nylon nut for standoff then a nylon washer, then your speaker wire clamped to the wire coming out of your speaker then a Wing nut holding it all together. I will have pics on my website soon. Wooden ones you will have to have someone make you some or very carefully use metal dies and taps using hardwoods such as oak or cherry. You can buy oak knobs that you can tap. Use mineral oil when cutting and go slow.
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"The only thing real is what you hear. Your senses tell you what is real.....not a scope or measurement tool. The NC1200 measures worse but sounds better"
Ric, that does not mean that measurements cannot capture what you hear - it just means that the correct things are not getting measured. . .
I am not surprised the NC1200 sounds better than the NC400 - and I don't believe it sounds better by accident! :)
Clearly the engineer designed something different in the NC1200 to optimize some kind of response - and that in turn should be measurable.
I am sure the engineer knows exactly what to measure - perhaps its phase response, group delay, whatever - but I am sure there is something measurable he is designing to.
So far the only measurements I have seen are distortion with static sinusoids (THD, etc)
So not surprised from these limited tests that no measurable difference is seen between amps - both exhibit distortion from static sinusoids that is in the noise floor
I would really be interested if someone had measurements of phase response and/or group delay. . .
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Bruno himself said he doesn't prefer one over the other.
I think we are in a transitional phase where we can now have utterly transparent amps but people are still expecting a "sound", so someone can be there to deliver it.
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Bruno himself said he doesn't prefer one over the other.
I think we are in a transitional phase where we can now have utterly transparent amps but people are still expecting a "sound", so someone can be there to deliver it.
From all the reviews I have read it seems everyone agrees the bass and mid-range are utterly transparent - but I see quite a few posts now regarding that the highs are not quite perfect on the Nc400
If that is the case (and I am just going by reviews here, haven't heard the nc400 myself) then that would not imply people expecting a "sound" but rather there is a lack of sound, which is very different. . .
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Everyone agrees the midrange is utterly transparent? That is not what I have read. I don't think the midrange is perfect. I think it lacks some body and involvement and also air at the top end. I expect modding and running them balanced will bring it around.
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(http://www.audiocircle.com/image.php?id=67667)
(http://www.audiocircle.com/image.php?id=67666)
Ric
The biggest imporovement you can do to this build would be to follow Bruno's very important directions per his data sheet.
Section 7.1
(http://www.audiocircle.com/image.php?id=67708)
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I could be wrong, but I don't think the output wires are anywhere near the AC or Power supply wires where they would interfere with the sound. "Biggest Improvement"?
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I could be wrong, but I don't think the output wires are anywhere near the AC or Power supply wires where they would interfere with the sound. "Biggest Improvement"?
I'll disagree. If Bruno says to twist them, I'd twist them no matter what. He has said it multiple times....
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I'll disagree. If Bruno says to twist them, I'd twist them no matter what. He has said it multiple times....
I must back jtwrace up on this one, I actualy heard the improvement after my (admittedly longer) speaker wires were twisted together in my UCD 400HGs (they were not close to the AC either) and I have no reason to believe it would be any different withe the Ncore.
Might as well do it what have you got to loose :thumb:
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I just ordered some nylon bolts,washes,nuts and wing nuts, that Ric suggested ,but I had to order a 100 of each which is way more than I could ever use, so if anyone wants to try these send me a buck or two( depending on how many you want) to cover postage and there yours, PM if interested.
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Everyone agrees the midrange is utterly transparent? That is not what I have read. I don't think the midrange is perfect. I think it lacks some body and involvement and also air at the top end. I expect modding and running them balanced will bring it around.
Exactly - the air at the top end is what I was talking about when I referring to the highs.
As far as the midrange I dont recall any critiques in that area but perhaps I missed that. .
In any case, I am very curious what kind of mods do you think would improve the top end?
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(http://www.audiocircle.com/image.php?id=67793)
(http://www.audiocircle.com/image.php?id=67792)
Here's another sorta-tweak implementation of an NC400/SMPS600 combo...
1. Tightly twisted AC cable, harness from SMPS to module, and speaker cables
2. Ric Schultz's speaker wire clamp setup
3. Hard-wired AC cable, based on a PC Ric used to sell
4. Shortened, almost minimal-length input cable
5. Some damping material on the case
6. Placed on a TipToe'd maple cutting block with Herbies Iso-cups between the block & the cases and various damping weights & dampers on the case top.
7. AMB fuses
I have them wired with Bruno's preferred input setup, but my sources are single-ended. So I modified my cables to replace the output side RCAs with XLRs.
I also played with power conditioning... I have a PS Audio Soloist filtered outlet available in addition to straight into the wall and can add Hammond Chokes as desired in parallel with the AC. The NCore started being plugged into the Soloist, but ended up straight into the wall with no chokes.
Although they showed some promise from a detail & control perspective at first, the musical presentation was not very coherent compared to a pair of B&O IcePower-based EVS 500M's from Ric. The highs/mids/lows did not gell into single notes, but seemed disconnected. Also the highs started out a bit harsh & hashy to my ears.
On the good side, bass was impressive in control & depth, although they didn't seem to go lower than the EVS 500Ms.
Now I've got 250-350 playing hours on the NCores... Better, very good in many ways. The note-level musical coherence has improved to where I generally don't notice a disconnect anymore. Mids-through-highs are cleaner, maybe still a bit emphasized compared to what I'm used to. The ultra-control of the bass has moved into the mids and they are very clear and lifelike.
But they are still not blowing me away... basically, they are still not making music for me. Overall musical coherent, flow, and urge is still not there strongly and is very dependent on the cleanliness of the powerline. Some of this may be the a bit of midrange body missing that others have mentioned. Then there's still a bit of emphasis and sometimes glare in the upper mids-treble.
When I put the EVS B&O Ice-Power-based EVS500M's back in, the musical coherence, flow, and urge come back immediately. The NCores are technically better amps... but I don't feel disappointed putting the 500M's back in. That's not a good sign!
I'm planning to give them more break-in time... I was reminded that some equipment takes a long time when I ran across a review of the Bel Canto REF500M's in Positive Feedback. The reviewer said:
"The mid-range became gradually textured, and lost for good a certain forwardness that waxed and waned with periodic irregularity during the early weeks; REF500M's treble region, that problem child, initially akin to a young one suffering of an unhappy combination of pulmonary insufficiency with whooping cough, happily healed from its youthful malaise whence the amplifiers approached 1000 hours of operation, and commenced to bloom into a delightfully lyrical maturity, almost devoid of residual constrictions.
Totally unforeseen, the steadily growing authority of the REF500M remained my greatest surprise. Well past the 1000 hours mark, at least until 1500 hours of music making, REF500Ms kept maturing in ease, a general sense of expansiveness, a surprising comfort in handling complex and intense dynamics, and a considerable solidity even in the most demanding fff (fortissimo) orchestral passages."
I also have the same experience as Ric reported with warmup. My experience with most gear since the early '80s has been a 1-2 hour warmup. The NC400/SMPS600 combo does not come on song for me until after 5-6 hours. So they are on most of the time (just down for system changes or threatened thunderstorms).
I'm trying to come up with additional changes that will improve the musicality while preserving the good points of the NCores. My thoughts:
1. Change the input & output wiring. Even though its not fashionable today, I've liked MIT hookup wire for its ability to maintain note coherence. I've got some raw input connectors coming in and will rewire both the inputs and the outputs when they get here.
2. Try different input stage power. I think it's worth trying a linear supply on the front-end and driver supplies, at the very least adding some additional filtering as serengetiplains did.
3. Output filtering. Instead of modifying the board as Ric intends, I'll start with an inline choke/resistor filter. If that makes a positive difference I'll try Econotweaks Detail Magnifiers.
4. EMI Reduction using conductive foam between the module & PS & around the PS.
5. Since they sound their best when the powerline is at its best, I've got a PS Audio P10 coming that theoretically should produce 'weekend-clean' AC quality all the time.
If these produce good results, then I'll bridge them... sharp eyes might have noticed that my case layout allows room for a second NC400/SMPS600 combo. OTOH, James Romeyn's comments on the sound quality at various load impedences has me concerned... I don't know the actual impedence versus frequency of this speaker as the manufacturer made a limited number of them and never published it, but I'm guessing it's a 4-6 ohm load across the spectrum. As I understand it, bridging could worsen any sensitivity.
And I am gathering the parts to do a balanced DAC source, but that's a while away at this time.
Some likely extended-work travel may get in the way of this further experimentation until late fall. But if it happens, I'll arrange to bring them along and lend them out in that area (more details once I'm sure that it'll happen).
Greg in Mississippi
P.S. My 'as-minimilistic-as-I-can-get-it' system consists of:
1. A computer music server based on cics's cMP/cPlay setup (see monster threads on Audio Asylum on this) with the latest OpSys slimming tweaks and all-linear computer, sound card, and DAC power supplies. The sound card is the digital section of an ESI Juli@ that has been modified within an inch of it's life and the DAC is a small ESS ES9022-based DAC card available from poster EUVL over at DIYAudio.
2. A series stepped volume control based on a Daven broadcast-quality multiposition switch and using a nude-Vishay as a series element. Cables from the computer are MIT 330 Shotgun and to the amp are just a very short twisted pair of MIT hookup and all are hard-wired to switch. I generally use the music player's built-in SW volume control and run this physical control at full volume.
3. The amps.
4. A pair of Eminent Technology LFT-IV speakers, a sorta full-range planar magnetic with rebuilt crossovers. Speaker cables are nothing-special Monster Powerlines hard-wired at the speaker end.
5. A bunch of various AC, damping, and woo-woo tweaks that most of you really don't want to hear about.
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You might want to try them with a balanced source like the designer has recommended before all the other things......
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Greg,
It is hard to tell from the picture but it looks like your power cable from the power supply to the amp module is twisted so tightly that it folds back on itself. Yes? If this is so then this is not good. Tight twisting is good but loops or folds are bad. You could untwist one or two turns and just have the cable stick up in the air a little bit.....then listen again and tell us what you hear....would be interesting to see if it makes a sonic improvement.
I will be modding/changing/lowering the values? of the output filter caps in about 7-10 days. I am also going to dremel off the top of the output connectors (the screw and nut are steel....not good) so I can solder even larger output wires directly down on the board next to the brass pieces that will still be left. I will report the sonic results.
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Just curious to know if anyone has tried using an all Alum. enclosure rather than steel. Second would it be prudent to use a separate enclosure for the power supply ? You guys may consider using compressed wool under the circuit boards for dampening. Worked well with projects for us. If you have a powercable that you can settle on hard wire it to the board and eliminate the IEC.
It would interesting to find out if a tubed input would make any difference with adding some body and soul.
charles
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Just curious to know if anyone has tried using an all Alum. enclosure rather than steel. Second would it be prudent to use a separate enclosure for the power supply ? You guys may consider using compressed wool under the circuit boards for dampening. Worked well with projects for us. If you have a powercable that you can settle on hard wire it to the board and eliminate the IEC. -SNIP-
Charles, thanks for the suggestions. My enclosure is aluminum (I almost NEVER use steel) and I do have the PC hard-wired SMPS. Also, I did not show it, but I do have some damping on the circuit boards and some of the larger caps. Violently agree with these! I will try some felt too, I saw this also from Mike Elliot's Alta Vista Audio site, but the couple of times I tried it before, I preferred using a combination of Herbie's Audio products and sheet-damping such as the 3-M & Dynamat.
I also agree on possibly a separate enclosure for the SMPSs. I really like the Genesis implementation of the UcD modules (see their website & the 6Moons Audio reviews of their amps), but I already had these enclosures & they seemed to be pretty good for a quick & dirty NC400 amp pair.
It is hard to tell from the picture but it looks like your power cable from the power supply to the amp module is twisted so tightly that it folds back on itself. Yes? If this is so then this is not good. Tight twisting is good but loops or folds are bad. You could untwist one or two turns and just have the cable stick up in the air a little bit.....then listen again and tell us what you hear....would be interesting to see if it makes a sonic improvement.
-SNIP-
I am also going to dremel off the top of the output connectors (the screw and nut are steel....not good) so I can solder even larger output wires directly down on the board next to the brass pieces that will still be left. I will report the sonic results.
Thanks for the feedback Ric, Yes, the power cord does have a loop that is held by that tie-wrap. I'm putting the NC400 back in the system today or tomorrow as the PS Audio P10 is coming on Tuesday & I want to get used to them again before installing it. I'll pull the tie-wrap & re-route the power cable without the loop.
Long-term, my intention is to shorten the power cabling and twist or braid the high-voltage cables with grounds separate from the low-voltage cables and control cables (and some corresponding grounds). My gut-feel is that any of this will have a minimal effect, but heck, it's very easy to try the re-routing.
On dremeling the output connectors, you are a very brave man! I know if I tried it, I'd have metal filings shorting my NC400 modules!
You might want to try them with a balanced source like the designer has recommended before all the other things......
Thanks for the suggestion, cab. But that's easier for you to say than me to do!
First, while I have a few other good digital sources, none are balanced. So I have nothing on-hand to try.
Second, I live in a fairly isolated and rural part of Mississippi... not much high-end audio I can borrow and try easily nearby.
Third, my options for making balanced sources are fairly sizable projects (each are MUCH bigger than all of NCore implementation changes I listed) AND I want to be sure any new digital sources are sounding like I want them before I use them to assess the NCore in a balanced vs single-ended mode.
Fourth, if I can only get the NCore to sound the way I want with a balanced source, I should give up on them now. ALL of my current & future-project phono stages are single-ended. More than 1/2 of the output stage options I have for future digital sources are single-ended. And I'm firmly committed to a minimalistic system with as few stages and connections as I can manage... my experence is that every stage adds its own sound and fidelity loss and that I get the best sound with only as many as I need to make it work and no more.
So I hear what you are saying, but if I can't get them to sound as I desire single-ended, they aren't right for my system!
All, again thanks!
Greg in Mississippi
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Update... the long-awaited PS Audio P10 arrived today. Neither the NCore or it are fully warmed up nor broken in, but I'm generally liking what I am hearing.
Increased mid texture & very smooth, inviting, 'golden' highs. Bass impact & dynamics may be diminished slightly and the lower mids thickened slightly, need to listen more.
Tonally, the NCore sound more like the IcePower-based amps now. But the detailing hasn't seemed to have diminished. Interesting!
What power conditioners have other used or has everyone else gone straight into the wall?
Haven't played with PCs or fuses yet... AMR fuse going in tonight, need to make up a short PC (only need about 18") & also try various combinations of straight into the wall or through the PS Soloist, with or without Hammond Chokes, etc..
Greg in Mississippi
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What power conditioners have other used or has everyone else gone straight into the wall?
I use a PS Audio powerplant premier. I like the quiet background, which makes it even more 3d. PS Audio highly recommended it for their icepower amps, which I had been using until the NCore.
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Here is a perceptive quote from another forum that may be worth taking to heart:
"The Ncores are very high end amplifiers. And with out a equally high end source, their true potential is never revealed. I believe in matching all the components in the audio chain with components of similar quality. The end result is only as good as the weakest link. "
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Here is a perceptive quote from another forum that may be worth taking to heart:
"The Ncores are very high end amplifiers. And with out a equally high end source, their true potential is never revealed. I believe in matching all the components in the audio chain with components of similar quality. The end result is only as good as the weakest link. "
Yep.
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I'll disagree. If Bruno says to twist them, I'd twist them no matter what. He has said it multiple times....
+1 Be sure to twist them in the opposite direction from the internal amp wiring, too.
<><
Dave
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This thread has been quiet for a while, so maybe I can get things going again. :D
I used two of the Silicon Ray enclosures for my build and started with inexpensive IEC connectors from Parts Express. This weekend I replaced the IEC with Furutech FI-10 Gs. It could be wishful thinking, but I think the Furutech are providing a cleaner, more open sound for my system.
I'm considering replacing the speaker binding posts next. Again, I started with cheap parts for Parts Express. I would be interested in opinions on whether this is a useful upgrade and what members are using for this connection.
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I found the IEC to make a nice difference as well. I was quite surprised as to the degree of difference. I also changed the fuse out when they went on sale at VH Audio and was pleased with that. I used Vampire binding posts, but did no comparison with others. Though down the road I will try what Rich had suggested. My wire came yesterday from Hypex. I hope to get it in today or tomorrow. :green:
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+1 Be sure to twist them in the opposite direction from the internal amp wiring, too.
<><
Dave
The reason for twisting them in the opposite direction is . . . . Or you are pulling our legs ?
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I found the IEC to make a nice difference as well. I was quite surprised as to the degree of difference. I also changed the fuse out when they went on sale at VH Audio and was pleased with that. I used Vampire binding posts, but did no comparison with others. Though down the road I will try what Rich had suggested. My wire came yesterday from Hypex. I hope to get it in today or tomorrow. :green:
I forgot to mention that mjock3 suggested the Furutech IEC in a PM. :thumb: On the fuse, which one did you go with?
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I went with the HiFi Tuning ones. Not sure how they compare to others.
Have you received the wire update?
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The reason for twisting them in the opposite direction is . . . . Or you are pulling our legs ?
He's not pulling your leg because it will reduce coupling and noise pick-up, but the difference will be very, very small.
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I went with the HiFi Tuning ones. Not sure how they compare to others.
Have you received the wire update?
Not yet. Will post when it arrives, and I get it installed.
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I forgot to mention that mjock3 suggested the Furutech IEC in a PM. :thumb: On the fuse, which one did you go with?
how about skipping the fuse...?
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how about skipping the fuse...?
:scratch: Are you suggesting removing the fuse from the power supply?
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This thread has been quiet for a while, so maybe I can get things going again. :D
I used two of the Silicon Ray enclosures for my build and started with inexpensive IEC connectors from Parts Express. This weekend I replaced the IEC with Furutech FI-10 Gs. It could be wishful thinking, but I think the Furutech are providing a cleaner, more open sound for my system.
I'm considering replacing the speaker binding posts next. Again, I started with cheap parts for Parts Express. I would be interested in opinions on whether this is a useful upgrade and what members are using for this connection.
I've used Eichmann ETI cable pods - in fact I also have these on my speakers. I've yet to find a better solution than these, they are well designed, they are easy to use, and sound just great.
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It has been a while since I posted anything regarding the NCore's. I have made a few improvements over the past month or so and though I would post what I did. I have my NCore mono's in a Sillicone RE2207 case with the very nice face plates that Jason (jtwrace) made.
I first replaced the power wires with a very nice set of wires that I sourced from a fellow AC member. He shall remain anonymous as he freely sent these to me.
I then replaced my IEC's with the Furutech FI-10 G's and also applied Soundcoat self-adhesive damping material where ever I could put it in the RE2207 case. (thanks Mark(mjock)).
I replaced the Mogami input wire with the "new & improved" stuff sent out by Hypex.
I ran my speaker hookup wire(DH Labs T-14) through a hole(along with a rubber grommet) I drilled between my speaker binding posts on the back panel and then used the Apex Jr. binding posts as a "clamp". (thanks Ric Shultz)
Lastly, I purchased a pair of Synergistic Research Quantum Fuses (thanks Anand)
The NCores with the above improvments are very satisfying. I have read plenty of remarks on the pros and cons of the NCores. However, with the changes I have made, these amps (to my ears) are very transparent. They draw me into the music and I don't want to leave the room. The NCores always were great in the bass. Tuneful and tight. However, the highs are now much more extended and the imaging is damn well spot on. I have yet to try different power cords and am still using a Volex on both amps.
After listening to the "new & improved" NCores for a while, I am trying some other components. I have inserted a Mytek DAC (thanks Ted_b :thumb:). I am using the analogue volume control on the Mytek which allows me to finally run the the NCores balanced via Ted's Furutech XLR cables. I have also inserted MG Audio Planus 2 speaker cable into my system. Lastly, I built(with Ted's help) a new C.A.P.S. V.2+ server (New Windows Platform) and am running JRiver V. 18.
Last week, I listened for the first time with this setup to some DSD recordings of Mahler's 2nd Symphony (Fischer conducting the Budapest Festival Orchestra) and some Beethoven Sonatas performed by Mari Kodama. My system has never sounded so satisfying. The synergy is fantastic. I have to also say that I have been a tube guy for years but I find this system to have the best of both worlds soundwise.
With the improvments I have attained, I might just entertain purchasing two more of the NCore's and possibly bridging them. However, for now, I will concentrate on choosing one of the new DAC's that offer DSD playback. After hearing DSD in all its glory, I can't imagine having a DAC without this capability.
Regards,
Randy
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OT, sorry...
Hey Randy. Would you mind describing your DSD sources and storage? SACD discs? Ripped files? If so, how? Where from?
Ever since hooking the balanced-outs of my OPPO right to the NCores, the sound is so good that now I am very interested in DSD DACs, etc.
Thanks for any advice.
Nick
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Nick:
Here are some threads related to your questions. These are located in the HiRez Circle:
Ripping SACD's to get DSD...
http://www.audiocircle.com/index.php?topic=95396.0
Taking SACD and BluRay directly to your DAC...
http://www.audiocircle.com/index.php?topic=82217.0
Some DSD capable DACS...
http://www.audiocircle.com/index.php?topic=110794.0
SACD sources...
http://sa-cd.net/home
www.amazon.com
Hope this helps,
Randy
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Thanks Randy, I really appreciate it...
Lots to research!
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what size fuse did you use, where did you get the sound coat?
thanks,
drmike
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Here is where I bought the Sound Coat...
http://www.partsconnexion.com/damping_soundcoat.html
You need a small (5mm x 20mm) 5A slow blow fuse.
Randy
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thanks randy.
drmike
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So, a little investigating: The nC400 speaker wire terminations appear to be a combination of materials. The screw is steel, and the the other parts are non magnetic, which makes me suspect brass. There are two ways I am thinking of dealing with this (I do not want the steel screw to be there, adding its own magnetic field). One, replace the steel screw with a brass one, or Two, remove the steel screw and brass square nut, and solder output wires directly to the header. I am really leaning toward the soldering approach, as there is plenty of surface area to achieve a nice joint, and a quality, well flowed solder joint is preferable to me.
Has anyone soldered speaker wiring directly to the header surface?
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Here is where I bought the Sound Coat...
http://www.partsconnexion.com/damping_soundcoat.html
You need a small (5mm x 20mm) 5A slow blow fuse.
Randy
What is the (theoretical) benefit of adding damping material to the amplifier ?
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Has anyone soldered speaker wiring directly to the header surface?
http://www.audiocircle.com/index.php?topic=110782.msg1144617#msg1144617
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What is the (theoretical) benefit of adding damping material to the amplifier ?
I will let others who know more about your question answer.
However, here are some links that discuss the question you ask...
http://www.gcaudio.com/resources/howtos/vibration.html
Here is a quote from Ric Shultz's website:
4. Try and eliminate vibrations anywhere you can. Constrained layer damping materials can be added to chassis parts, heat sinks, heat sink tabs on transistors, circuit boards (you do not want any damping material put directly on top of signal carrying parts or traces). Doing so would add the sound of the damping material (dialectric absorption) to the signal. Of course, you want to use the best feet and shelving under your equipment.
I am sure that you could google and find other sites that talk about the benefits of using damping materials in metal enclosures. Did the damping material help in my case? Dunno. Did it hurt in my case. Certainly not and for a $12 investment for 2 sheets I figured why not try it.
Regards,
Randy
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OT, sorry...
Hey Randy. Would you mind describing your DSD sources and storage? SACD discs? Ripped files? If so, how? Where from?
Ever since hooking the balanced-outs of my OPPO right to the NCores, the sound is so good that now I am very interested in DSD DACs, etc.
Thanks for any advice.
Nick
Nick,
The DSD files were a gift from me (Randy and I have been diligently working on his system and I felt a couple DSF examples were appropriate). I have my entire SACD collection (about 830 SACD's) ripped to DSF, and have written an SACD Ripping Guide for Dummies pdf primer that I've distributed to hundreds so far. Feel free to PM me and I'll send out the pdf and the links to get started.
DSF files (DSF format used because it supports full ID3V2 metadata/tagging) are slightly smaller than 24/176k PCM files, so storage is about the same as PCM high rez on average. And ISO's are also part of the ripped process, which are great for archiving in case yous cratch an SACD or for later DSD multichannel extraction too (that's a project for later).
I have roped another DSD fan. :thumb: YES! :D
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I have roped another DSD fan. YES!
Yes...yes you have.... (Sorry Jason...no more DSD talk in the NCore thread... :icon_lol:)
Randy
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http://www.audiocircle.com/index.php?topic=110782.msg1144617#msg1144617
Thanks jt, I have seen Ric's mod. He removes the terminal, to make room for his cap mod. I was just wondering if anyone has soldered speaker wiring directly to the existing terminals: removing the screw and compression nut, sticking the wire through the hole in the terminal, and then soldering down to the surface of the terminal. From looking at it, it appears that this would make a good connection. Just have to be careful to not overheat surrounding components, but the wire itself would act as a pretty good heat sink.
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Thanks jt, I have seen Ric's mod. He removes the terminal, to make room for his cap mod. I was just wondering if anyone has soldered speaker wiring directly to the existing terminals: removing the screw and compression nut, sticking the wire through the hole in the terminal, and then soldering down to the surface of the terminal. From looking at it, it appears that this would make a good connection. Just have to be careful to not overheat surrounding components, but the wire itself would act as a pretty good heat sink.
I see. At that point why not just use bare wire? That's what I do and it works very well and you don't make a mess of the terminal. Some DeoxIT and you're good to go.
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How could you possibly use "Constrained Layer Damping" on an already built chassis? As CLD requires two of the same sized panels with the damping compound in between.
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:scratch: Are you suggesting removing the fuse from the power supply?
replace it with a solid silver or copper or silver/gold. :lol:
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How could you possibly use "Constrained Layer Damping" on an already built chassis? As CLD requires two of the same sized panels with the damping compound in between.
The constraining panel does not have to be the same size as the structural panel you're trying to damp. What was described earlier, however, was not constrained layer damping, but rather free-layer damping. This paper (http://www.earsc.com/pdfs/engineering/understandingdamping.pdf) provides a nice overview of the two methods and relative effectiveness, but does not address the impact on resonant frequency. This paper (http://www.cs.wright.edu/~jslater/SDTCOutreachWebsite/vibration_suppression_banner.pdf) addressed the frequency shift in one plot and covers several other damping methods besides, although not likely to be employed in audio.
Sticking rope caulk to the inside of chassis panels provides one of the simplest means of free-layer damping. I'd be curious to see how well green glue sticks to metal, as green glue coupled with some vinyl tile or another high density (but non-resonant) tile would make for a rather simple CLD system.
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"brj" your second link seems to have gone missing.
Two things about "green-glue":
a] It's not glue.
2] It starts out life with a texture much like peanut butter and it remains that way.
I'd be curious to see how well green glue sticks to metal, as green glue coupled with some vinyl tile or another high density (but non-resonant) tile would make for a rather simple CLD system.
That's not a CLD system.
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Link corrected.
I don't wish to divert this thread, but a CLD system has a constraining layer and a viscoelastic layer mounted to whatever surface you're trying to damp. Green glue is a viscoelastic polymer with sufficient adhesive qualities to permanently attach 2 layers of drywall together in its usual application, which leaves me comfortable with their description of it being a "glue". Thus, in my example, Green Glue forms the viscoelastic later and the vinyl tile forms the constraining layer (reacting mass). This forms a CLD system.
Again, the Sound Coat that rklein used is an example of free-layer damping. I haven't tried Sound Coat, but I've used rope caulk in a similar application, the very "ringy" steel chassis of an external power supply. I actually have enough space in that chassis that I may eventually get around to trying a CLD solution on the inside of the upper surface, though the rope caulk was an obvious improvement. (An improvement based on the knuckle test, at least. If I make the CLD change later, I'll use the accelerometer app in my phone to get better feedback, if still far from precise.)
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are you referring to this http://www.greengluecompany.com ?
I have two layers of green glue sandwiched in my bedroom, and, it doesn't really help. I could feel the wall shaking even music was just played at moderate volume (sound was also leaked from that wall). I personally believe concrete walls work much better, or thick metal layers at your ncore case.
recently I have suspended the amps with magnetic levitation and it works very well! :thumb:
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In the home theater forums I have read countless threads and many, many posts from Ted White about Green Glue. These threads make it very clear the Green Glue is NOT an adhesive and the drywall(sheet-rock) must be joined by screws. A good CLD systems requires that both outer panels by of the same size shape and material construction. That is two 1/2 inch drywall panels are better than one 1/2 & one 5/8 panel.
If you are going to do a project like this, I suggest using Liquid Nails- Sub Flooring Adhesive, which is an adhesive and is more readily available in small quantities.
I don't believe that this project will make any different with any stock Ncore product.
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I see. At that point why not just use bare wire? That's what I do and it works very well and you don't make a mess of the terminal. Some DeoxIT and you're good to go.
JT: here is why: 1. I would like to avoid a steel screw in close proximity to the wiring. Any steel will develop a magnetic field due to the AC current, and this magnetic filed could produce distortion. Many high end companies go to great length to avoid additional magnetics, especially directly in the signal path.
2. A screw terminal connection is never perfect, the only pressure connection which can be perfect is one where the connection is crimped by a hydraulic press, actually producing a cold weld between the materials. If one can have a true hydraulic crimp and cold weld, that is the best connection, next best is a pressure crimp followed by solder (to fill in gaps and eliminate gas penetration). Any air gaps in a connection will induce some noise/distortion, as electrons in their chaotic ways will jump the gaps, with noise caused by the jump.
3. I would prefer not to use non-insulated, stranded wire, as the same electron jump noise will happen as electrons move across the gap from strand to strand. Large gauge solid core is out because of skin effect problems. I prefer to use litz wire (Cardas) to avoid these problems. Litz wire is best terminated by solder, as it has to be tinned anyway to use, and the tinned wire end will not make a great connection with the stock nCore screw terminal.
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How could you possibly use "Constrained Layer Damping" on an already built chassis?
Hmmmm... Well, I peeled off the thin layer of cellophane and applied with minimal pressure to the metal surface.
Am I to expect a visit from the CLD police in the middle of the night for the perceived misuse of this product? :dunno:
Seriously... with all due respect, the damping material that I used certainly did not hurt my NCores. And maybe, just maybe they might have helped. As I stated earlier, for $12, I tried it. I certainly did not expect 5 additional posts devoted to the pros/cons of this subject.
On another note, if someone has soldered their speaker wire and got rid of the screw as Barrows has posted about, I would like to know as well. Especially, any technique you wish to share.
Regards,
Randy
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JT: here is why: 1. I would like to avoid a steel screw in close proximity to the wiring. Any steel will develop a magnetic field due to the AC current, and this magnetic filed could produce distortion. Many high end companies go to great length to avoid additional magnetics, especially directly in the signal path.
The slight possibility of this happening is restricted to very sensitiy circuits with high impedance's and very low signal levels. Nothing like that in a power amplifier.
3. I would prefer not to use non-insulated, stranded wire, as the same electron jump noise will happen as electrons move across the gap from strand to strand. Large gauge solid core is out because of skin effect problems.
While Class "D" amplifiers do have high switching frequencies where skin effect does come into play, the circuit designer does understand this and takes it into account.
I prefer to use litz wire (Cardas) to avoid these problems.
Skin effect is not a problem at speaker cable frequencies and sizes.
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I prefer to use litz wire (Cardas) to avoid these problems. Litz wire is best terminated by solder, as it has to be tinned anyway to use, and the tinned wire end will not make a great connection with the stock nCore screw terminal.
Yes, never use solder-tinned stranded wire with a screw terminal. With time the solder will cold-flow and the screw will loosen.
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In the home theater forums I have read countless threads and many, many posts from Ted White about Green Glue. These threads make it very clear the Green Glue is NOT an adhesive and the drywall(sheet-rock) must be joined by screws. A good CLD systems requires that both outer panels by of the same size shape and material construction. That is two 1/2 inch drywall panels are better than one 1/2 & one 5/8 panel.
My reference to drywall was only made to mention Green Glue's most common application for those unfamiliar with it, not to suggest that how it is applied on drywall is how it should be used in any other potential application, whether CLD or otherwise. Certainly if you screw what would otherwise be your constraining layer to the layer to damped, through your viscoelastic layer, you've now coupled those layers and you no longer have as effective a CLD implementation. (Many would argue that such a coupled system is no longer CLD implementation at all.)
For what it's worth, I double checked with one of the senior guys in our Loads and Dynamics group at work today to make sure I wasn't misspeaking. Damping of acoustically induced bending modes relies more on a constraining layer that is very stiff (but can actually be very light and thin), whereas the damping of lateral modes can rely more directly on the mass of the constraining layer. The degree of benefit realized by increasing the coverage area of your constraining layer relative to the surface to be damped will thus depend on which modes you're more concerned about, though CLD can be effective even with fairly minimal coverage.
rklein, my apologies. Your free-layer damping approach is entirely effective, and I only sought to clarify why your approach was effective, if differently so, than a CLD based implementation.
Mods, please feel free to remove my posts if they are too distracting. Thanks!
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I just noticed that Green Glue should only be used in rooms below about 85°F, so keep it away from vacuum tube amplifiers.
http://www.greengluecompany.com/faq
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rklein, my apologies. Your free-layer damping approach is entirely effective, and I only sought to clarify why your approach was effective, if differently so, than a CLD based implementation.
I appreciate it but no apology is needed. 8) I was just busting Speedskater's cajones a bit in good fun.
Randy
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I ended up removing the speaker wire terminals entirely, as they are brass, and I do not want a low conductivity material like that for my speaker connections. Now I can solder the output wiring directly into the PCB itself.
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I ended up removing the speaker wire terminals entirely, as they are brass, and I do not want a low conductivity material like that for my speaker connections.
What are you using for speaker binding posts at the amplifier rear panel and at the speaker enclosure input to avoid brass in the circuit?
Steve
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Steve: Amplifier binding posts are going to be Cardas copper with silver/rhodium plate. My speakers are Focus Audio FS-888s with Cardas copper binding posts with gold plate. I see lots of folks choosing nice copper binding posts in the nCore build thread, I just feel brass, at 28% the conductance of copper, seems like a bit of a compromise for such a low output impedance and low distortion amplifier. Really is too bad that Hypex did not just use a copper terminal, or just some beefy plated through holes on the PCB for direct soldering.
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I went ahead and replaced the skinny stock input wiring for the SMPS 600s with 15.5 AWG Cardas litz. These are direct soldered into the boards, and to the IEC connector. It does seem that the result is better slam, and more body/bass weight at higher volume levels. The stock 18 gauge wire and relatively weak connector always "bothered" me… I certainly feel this was worth the effort.
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The reason for twisting them in the opposite direction is . . . . Or you are pulling our legs ?
Simple physics/electronics/RF practice with small returns. You are there. It is easy to do. Why not do it?
Dave
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I replaced the input and power wiring from hypex with occ silver served with cotton. The input wiring is an 8 conductor helical weave. I also used dual 16 ga occ silver wire served with cotton for the speaker wire leads. Sounds good to me.....
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Ric
The biggest imporovement you can do to this build would be to follow Bruno's very important directions per his data sheet.
Section 7.1
(http://www.audiocircle.com/image.php?id=67708)
Kimber Cable is big on braiding over twisting.
Would braiding be better than twisting (including the multi-wire harnesses)???
TIA
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Would braiding be better than twisting (including the multi-wire harnesses)???
Braiding tends not to be as compact as twisting. You want to minimize the space between the wires.
Twisting is used to minimize interference and stray fields. Braiding is used to minimize skin effect (in litz wire etc.) mainly to improve transmission of high (but not too high) frequencies - not an issue with things like power connections.
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Braiding tends not to be as compact as twisting. You want to minimize the space between the wires.
DEpends on the braid geometry. Some can be compact.
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DEpends on the braid geometry. Some can be compact.
Sure - but what is the supposed benefit of braiding in this case?
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same as twisting.....had a bunch of 28 gauge occ wire so I used an 8 conductor braid. Didn't think the 28 gauge was enough to simply use one conductor for each signal.
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same as twisting.....had a bunch of 28 gauge occ wire so I used an 8 conductor braid. Didn't think the 28 gauge was enough to simply use one conductor for each signal.
Fair enough - but braiding is not as efficient as twisting in preventing EMF pickup/radiation. The whole idea of twisting is balancing two cables so that they have exactly the same twist and are as close together as possible, so that they balance out each other. With the 8 conductor bunch, you would probably be better off with twisting them in pairs.