AudioCircle
Audio/Video Gear and Systems => All Solid State => Topic started by: jeffreybehr on 28 Feb 2012, 09:52 pm
-
Received them yesterday, opened them to be sure there were no loose parts, and fotografed them. Got them running. Their lite-gray faces match my Porsche Arctic Silver V'steen 5Bs very well, to the point that the champagne-faced Marantz MA-24 driving the CC looked quite out of place; I reinstalled the much-improved Marantz MA-500 and voila! (But I MUST do something about those light-maple amppads!)
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/750swarmingw500CC_1280w.jpg)
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/R-champopen_1280w.jpg)
For those who don't know, the '750, like at least the DNA-500 and perhaps many predecessor McC amps, is fully differential/push-pull. That means that there's a positive-polarity push-pull amp section 'pulling' and a negative-polarity push-pull amp section 'pushing'. Note one speaker-power lead coming from one side of the board and going to one (let's call that positive) binding post (and then its twin, as the amp wears 2 pairs of posts) and also another speaker-power cable coming from the other side of the amp and to its call-it-negative bindingpost.
Altho I'm no quick-to-hear-differences GEA, the sounds are a little less harsh in the hi frequencies based on a couple discs I listened to carefully with only about 5 hours on the amps.
More later. :thumb:
-
Nice score!
I was looking at those eariler. They seem like they could easily power any speaker quite nicely.
Please let us know you impressions as they break in.
-
Congratulations! Let us know how the break in goes. Enjoy!
Joe
-
Awesome! Keep those babies powered up 24/7 :thumb:
-
Thats lots of power. Enjoy your setup!
-
So, I'm not the only one who opens new gear up for a look inside and take a few pics before hooking it up?
Beautiful amps, enjoy.
-
Look forward to further comments!
Congrats
Mark
-
Go baby!!
-
I'm eager to hear your thoughts after a couple of weeks. The DNA-750 was on my short list when I ran across a deal on a Moscode. I may still end up there one day.
Scott
-
Those are very nice amps, you're going to love them with your Vandersteen 5's...
-
Couldn't resist. :icon_twisted:
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/Face_1280.jpg)
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/Toplookingfront_1280w.jpg)
-
With about 50 hours on them Wednesday evening--they're cookin' 24 hours/day with fullband pinknoise--they continue to sound quite good. Tonally, they're very...full-bodied, very whole sounding. I continue to operate them and the speakers without the 1- and 1.5-Ohm resistors I had been driving the upper frequencies of the V'steens with, and the treble frequencies still sound quite there but not too much there. Sorry for the lame descriptions.
I'm really happy so far. Don't know if I'll last a month without replacing the Nichicon-brand 'DNA' caps with BlackGates. 8)
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/DNAcapsclose_1280w.jpg)
The 4 smallish 'lytics close to the output transistors are, in my 2nd (?) version of the DNA-750, 470/100 Nichicons, each of which is bypassed with a 0.47uF 715-series OrangeDrop film cap. (Rail Voltage is 61V.) I'll be replacing them with 680/65 BlackGate-Ns, quite affordable here... http://www.partsconnexion.com/cgi-bin/sc/productsearch.cgi . Since the bottom cover is removable, it ought to take no more than an hour to do that. :)
-
good luck ever getting those amps serviced at CJ in that case...
Personally, I'd leave well enough alone and enjoy the amps
:)
-
Looks good! Definitely replace the fuses with some Hi-Fi supremes
Wig :thumb:
-
good luck ever getting those amps serviced at CJ in that case... Personally, I'd leave well enough alone and enjoy the amps
:)
I understand that attitude, I don't argue with anyone who chooses it, and I know that those folk enjoy their music systems as much as I do. But that's not my attitude. Parts costs affect the retail price of all manufactured goods, and I can afford to improve parts myself, but I couldn't afford to buy the amps if they cost maybe $3 or $4K/pr. more. So I'll just improve some parts while NOT changing the circuitry. Here's one little corner.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/PairofBGsSCP_1280w.jpg)
The new 'lytics--the 'DNA' caps--are Blackgate-Fs, 680uF, while the film-type bypass cap is a 1uF SoniCap Platinum (Teflon). As improved, each 470 (times 8 per amp) will be a 680uF BlackGate, and each amp will have 4uF of Platinums instead of 3.76uF of OrangeDrops.
-
those look pretty cool! Why did you choose Orangedrop caps? Never heard of em.
-
those look pretty cool! Why did you choose Orangedrop caps? Never heard of em.
I didn't; c-j did. I'm replacing many of them with SoniCap Platinums, 5-star-quality Teflon-film caps.
Orangedrops are (were?) made by Sprague for decades and are good-sounding caps, but they're sure not as good as lots of modern caps.
-
Here's what a full side looks like with the BlackGate 'DNA' caps and SoniCap Platinum bypasses.(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/L-chLsideBGsSCPs_1280w.jpg)
The rear and bottom panels rang a bit, and since I obsess about this stuff, I applied chunks of the thicker SoundCoat to the rear's inside and the bottom's outside. The upper strip here is a 2nd layer.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/SoundCoatinsideback_1280w.jpg)
Got almost a full sheet (which is 12"-by-13-1/2") on the bottom.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/BottomwithSoundCoat_1280w.jpg)
BTW, the 'smears' of white stuff on the sides of the Platinums are remnants of the double-sided plastic-foam 3M mounting tape I use on these things. Sometimes it all comes off easily, and sometimes not. I prefer not to scrape too much on the sides of caps, since the outer tape is quite thin.
The system sounded glorious last nite playing BIS's newish recording of Smetana's Ma Vlast (My Fatherland) performed by the Malaysian Phil. O. and Claus Peter Flor. This is a 5-star performance and recording that sounds very natural and real on my MC system. Here http://www.sa-cd.net/showtitle/6877 are some comments on this recording.
-
My goodbuddy came over today and rebuilt the frontend powersupply. The output caps were a pair of 470/100 Nichicons bypassed with a pair of 0.47 O'drops. The new caps are 470/160 BlackGates, bypassed with four 0.47uF SoniCap Platinums (Teflons). We also removed another pair of 0.47 O'drops to make room; those bypassed the feedback-loop shunt caps, huge 30uF c-j 'propylenes. I'll replace those bypasses later.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/Frontend-PS2_1280w.jpg)
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/Frontend-PS1_1280w.jpg)
Things are moving along. :)
-
Looks like a lot of fun :thumb:
-
Have done a bit more--
1. Higher-quality Cardas bindingposts...
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/10March12_newbindingpostsoutside_1280w.jpg)
...these being CCGRs which means copper nut/copper body/gold-plated nut/rhodium-plated body;
2. Added more SoundCoat to the bottom...
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/10Mar12_BottomwithSoundCoat_1280w.jpg)
(I SuperGlued the Herbies' Tall Tenderfoots to the cover, but that didn't work, so they're again loose.
3. Replaced the four-per-amp 470pF RFI-filtercaps around the driver transistors with Rel-Cap RTEs...
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/09Mar12_ampbottom_1280w.jpg)
...the little black rectangles in the corners. The double-quad of o'drops flanking the powertransformer will be coming off.
4. Applied more SoundCoat to the inside and outside of the rear panel...
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/10March12_newbindingpostsinside_1280w.jpg)
Have replaced a few other O-drops and will end up with only 1 very small pair plus the bypasses on the frontend-supply's 1st-pole caps in each amp.
Will be replacing the RCAs with Furutech FP-901Gs but only after I receive the final input-filter caps and resistor. I'm not looking forward to that work, as there's not much room down there and the rearpanel looks as if it doesn't move to the the rear very far.
Am now scheming on a continuing and even-better improvement of the output-stage powersupply, with I-hope-double the amount of BlackGate-N 680/65s as DNA caps and, eventually, higher-quality initial-PS caps.
The amps continue to sound supergood with the V'steens, and I expect they'll get better as all these new caps, etc., break-in.
-
Got the new input-filter caps and resistor installed. I chose equal values (0.01uF) of SoniCap Platinums (for clarity, cleanliness, detail) and Jupiter HTs (for wholeness and slight warmth). With the initial PRP-brand 120K series resistor, the high-pass-filter point (HPFP) is 58Hz. Installed them inside the amp.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/13Mar2012_inputfilter_1280w.jpg)
The 120K resistor reduces the amp-system Voltage gain by 18.7dB which gets my preamp's level control close to as high as I want it. I might order and install 150K resistors for a little less gain and which will move the HPFP to about 48Hz.
-
Jeffrey,
It is amazing what you are able to do with these amps. Thanks for sharing!
Joe
-
Jeffrey, It is amazing what you are able to do with these amps. Thanks for sharing!
Joe
TY, and YW. There's more to come, and I'll continue posting pics and comments. These amps are naturals for my kind of parts-replacement projects--there's lots of space within, the circuitboard is strong and the traces fairly large, and the bottom cover comes off. All that makes it fairly easy.
-
That does look like a lot of fun. I hope to be able to tinker the same way soon, beginning with my next amps. The only hands on I've had so far was building crossovers.
-
When do we get to hear about the sonic improvements? I did some upgrading on an older Harman Kardon amp and believe I heard significant improvements. Let us know your results, curious minds want to know.
-
So when all was completed to date: How much did the upgrades cost and can a relatively competent audio eng perform the mods? Does C-J offer the mods when sent the amps?
Thanks for the comprehensive step by step!
T
-
So when all was completed to date: How much did the upgrades cost and can a relatively competent audio eng perform the mods? Does C-J offer the mods when sent the amps?
Thanks for the comprehensive step by step!
T
I've not thought about it so I have no idea what the total cost so far is. Probably it's not as much as one might think since the excellent BlackGate 65V. caps I'm using in the DNA positions are only $13 each.
Certainly an audio eng(ineer) could do what I've done; I'm not even a trained technician, I'm merely an audio hobbyist.
I can't imagine c-j doing the custom stuff I've done, but independent audio-equipment techs certainly could. What I've done is really simple stuff--literally removing the medium-quality parts and installing HIGH-quality parts.
I'll continue to post my changes.
-
When do we get to hear about the sonic improvements? I did some upgrading on an older Harman Kardon amp and believe I heard significant improvements. Let us know your results, curious minds want to know.
I am NOT a quick-hearing-of-tiny-differences golden-eared audiofile; sometimes I think I'm more a tin-eared audiofool...and I'm definitely NOT an audiofile who describes sonic changes with BIG words...you know the ones...'black and white'...'huge'...and my favorite, 'totally different'. I believe that all these changes are for the better and that eventually I'll perceive an audible improvement in my system. Sorry I can't be more specific.
-
There might not be such a thing as "golden ear" anyway. Might all just be marketing for gear companies. There is either you can hear so high or you can't.
IMO, after everything I've seen as a noob, there should be a reality series called "American Greed: Audiophiles" and show just how much stuff gets bandied about as legit technology is nothing but a SCAM SCAM SCAM.
-
I'm especially curious why you removed the transformer coupled input and replaced it with a cap and resistor? Was that to get better synergy with your preamp?
I know there is a limitation on matching impedance pre to amp on the DNA 500 (which I own). Is it the same for the 750?
-
I'm especially curious why you removed the transformer coupled input and replaced it with a cap and resistor? Was that to get better synergy with your preamp? I know there is a limitation on matching impedance pre to amp on the DNA 500 (which I own). Is it the same for the 750?
I didn't remove the transformer--it's still there, on the right of the pic in post #21 and here in a pic of the 2nd amp...
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/14Mar2012_inputfilter2_1280w.jpg)
...along with its multicolored wiring. If it weren't, half the amp wouldn't work, since the transformer creates the opposite-polarity signal to drive the 'other' half of the amp. I added the series resistor and pair of caps before the transformer's input.
The goals of this RC network are to:
1. Increase the amp's input impedance so that it and the bass amp's input impedance, paralleled, is easier to drive and also to keep the high-pass filterpoint of the preamp's output-coupling caps below 2Hz;
2. Create a much higher resistive value for the input-filter caps to work with. The amp's nominal 10K input impedance would have required a larger cap value to achieve a HPFP in the 50H - 60Hz range. BTW, I've calculated, using signal generator and Voltage meter, etc., that my amp's input impedance is 16.7K-Ohms. This determination was so accurate that when I calculated that 0.02uF and 120K (added) would create a 58Hz FP, and that's exactly (within 1Hz) what I got after installing those parts.
3. Reduce the poweramp system's Voltage gain so that I can use my preamp's volume control in the gain, rather than cut, range. The 120K resistor cut poweramp gain by almost 19dB, but my preamp, a multichannel c-j MET1, still has maybe 15dB of gain left unused. IOW, I still operate the preamp at average levels of -15dB to -25dB.
So the input transformer is still there, 'splitting the phase' or, more accurately, creating an negative-polarity duplicate of the positive-polarity signal.
And yes, that preamp-to-poweramp impedance 'matching' problem did exist, especially with a 67K load in parallel*, and is eliminated by adding the resistor. You too can do that with your '500. Of course, the higher resistor value you choose, the more it drops Voltage, which requires higher Voltage drive from the preamp. Passive 'preamps' need not apply, as the combination of low-gain poweramps driving relatively low-sensitivity speakers requires high-gain frontends. :|
Another interesting (to me, at least) thing about this/these amps--altho they're fully differential/'balanced'/push-pull, the positive-and-negative-signals feature of a 'balanced' input using an XLR connector is not used. Only the XLR's positive lead is used, joined to the RCA's positive input at the RCA's positive terminal.
* yielding an actual 13.4K-Ohms
-
I know you bypassed all the chips on the output board with Sonicaps. Here's a trick I learned from Bob Crump when he voiced the JC1. I did this on my DNA .5 when I upgraded it many years ago (using RelCap RT's which is what he used at the end of the rail on the JC1 to bypass the Nichicon's).
BC suggested not putting bypasses on all the output devices. Instead he suggested bypassing only the "inner" chips (closest to signal origination) and leaving the other half / output side chips alone. His feeing was that too much of a good thing was too much, and this was a nice balance.
Just a thought in case you find that things sound too open afterwards and need to tweak it.
-
Got and installed the final parts before I tackle the DNA-cap expansion, which will at least triple the 680uF-times-8-per amp.
The top shows:
1. The new speakercable, composed of 1 strand of Neotec UPOCC 18g. copper plus 2 strands of 20g. silver in Teflon airtubes, per pole;
2. Just how few capacitors are left on the top of the board; and
3. The new Furutech FI-10(R) IEC power inlet, this time a screw-type instead of solder-type.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/15March2012_top_1280w.jpg)
The bottom.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/15March2012_bottom_1280w.jpg)
The only orangedrop bypass caps are on the 1st pole of the frontend PS. The 4 medium-sized white caps are the output-section fuse bypasses, now MultiCap RTXs.
-
What sort of camera are you using to take these excellent close up shots?
-
What sort of camera are you using to take these excellent close up shots?
Good question! The pics are wonderful.
-
TY, gentlemen. :)
I use a Canon 5D and, virtually always for this kind of stuff, a Canon 24-105/F4/IS/L lens. Sometimes I need to add a 12mm extension tube for shots closer than, say, a foot from the lens.
I have several daylight-balanced (c. 5K color temp.) flourescent floodlites that I use for working on and fotografing the amps, and I positioned about 4 for these shots. I also use a Canon 420EX flash rotated to bounce off a wall/ceiling. Almost all of this stuff is shot handheld--and the Image-Stabilized lens REALLY helps eliminate camera shake--altho sometimes I use a 'monopod', that being a stick about 4' long on which I rest the camera. I use Photoshop CS 5 (PS 12) to develop the images.
One 'secret'--NEVER position the camera squarely above or in front of a reflective surface you're fotografing...unless you want a HUGE, bright reflection in the images. For these 2 shots, I positioned the camera above the rear panel--the front edge of one sandal is barely visible in both. Cropping in PS using the Perspective control eliminates the the nonsquareness of the square that occurs because the rear of the rectangle is farther away from the camera than the front.
Here's 'The Lab' and 'foto studio' with one of my little Marantz MA-22s serving as the victim.
(http://i89.photobucket.com/albums/k220/jeffreybehr/Marantz%20M-22/16March2012_TheLab_1280w.jpg)
Visible are 3 work/fotofloods plus my reading lamp moved into position.
-
Good job. Thanks for sharing!
-
I like in your photo that I can see your "fan" is off the grid - LOL. Forgetting that little joke, thanks for sharing and good luck; nice skill set you possess.
-
TY, gentlemen. :)
(http://i89.photobucket.com/albums/k220/jeffreybehr/Marantz%20M-22/16March2012_TheLab_1280w.jpg)
Visible are 3 work/fotofloods plus my reading lamp moved into position.
Looks like a Conrad Johnson CT5 in the rack...NICE!
-
Looks like a Conrad Johnson CT5 in the rack...NICE!
Actually it's my 6-channel version of the CT-5...sort of. It's an MET1...
(http://i89.photobucket.com/albums/k220/jeffreybehr/C-j%20equipment/Inrackclose_800w.jpg)
...now discontinued, and is of the 'propylene-and-'styrene generation. New, it sounded very nice if not the most-transparent preamp in the world. I've replaced the front-L&R output-coupling caps with Sonicap Platinum (Teflons)...
(http://i89.photobucket.com/albums/k220/jeffreybehr/C-j%20equipment/11Nov2010_SCPcouplers1_1280w.jpg)
...and have replaced the 1st- and 2nd-pole PS-output caps with Jupiter HTs bypassed with small Platinums.
(http://i89.photobucket.com/albums/k220/jeffreybehr/C-j%20equipment/11Nov2010_PS2_1280w.jpg)
It now sounds VERY good...more transparent and cleaner than the original. Soon I'll be replacing the centerchannel's output-coupling combocap with a MultiCap RTX ('styrene) bypassed with small Platinums.
------------------------------
...and replace it I have.
(http://i89.photobucket.com/albums/k220/jeffreybehr/C-j%20equipment/20March2012_CCcouplernew2_1280h.jpg)
That's a 2/200 MultiCap RTX bypassed with a stack of SoniCap Platinums totaling 0.155uF.
-
Thanks for sharing Jeffrey! Awesome job on the amps. I appreciate the updates along the way. Please keep it up.
Joe
-
Actually it's my 6-channel version of the CT-5...sort of. It's an MET1...
(http://i89.photobucket.com/albums/k220/jeffreybehr/C-j%20equipment/Inrackclose_800w.jpg)
I hope you don't listen at "70 - 70" I've owned a CT5 and now an ET2 and the loudest I listen is "60", but if you're driving 5 or 6 speakers perhaps it requires more umph?
-
I hope you don't listen at "70 - 70" I've owned a CT5 and now an ET2 and the loudest I listen is "60", but if you're driving 5 or 6 speakers perhaps it requires more umph?
I listen at settings as high as in the 90s, intentionally. Somewhere in my above-ramblings about poweramps, I wrote that I've reduced the Voltage gain of my poweramps by almost 19dB just so that I can run my preamp in its gain range instead of its cut range. (It has 25dB of gain, and the level-control range is 99-1/2dB, so at any setting below 75, it's cutting the input level, and at any setting above 75, it's boosting the signal.) The typical range for music is 70 to 85.
The principal determinants of level-control setting is poweramp gain and speaker sensitivity...and, of course, listening level desired.
-
Jeffrey,
Enjoying the music?
Joe
-
Jeffrey, Enjoying the music? Joe
Indeed I am. The music is full, rich, detailed, effortless. Just ordered the last batch of 65VDC BlackGate-Ns to increase the highest-quality energy storage at the DNA positions, and a quad of 1/100 RTXs are on the way to replace the quad-each of OrangeDrops on the boardbottom.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/15March2012_bottom_800w.jpg)
Apparently these bypass caps ought to be filtering hi-frequency noise, and I was advised that the RTXs are better at that than the O'drops.
And YOU are enjoying your new Premier 350SA, JG?
-
And YOU are enjoying your new Premier 350SA, JG?
Oh boy am I !!! That is one amazing amp. I do think she needs some break in. After 4 years in hibernation and not sure what came before that, I sense a little forwardness in the treble region. I hope as the caps break in and I get more time on it, things will come together. The bass is bottomless and the musc seems to want to explode from the speakers. Just beautiful. That glorious CJ midrange and layering is right there in full glory. All I need now is to match it up with a GAT and I'll be home free.
Thanks again my friend. Your skills (in photography and audio) amaze me.
Joe
-
Your skills (in photography and audio) amaze me.
Ah...shucks...
:oops:
-
Bought a quad of MultiCap 1/100 RTXs and replaced the quads of 0.47uF O'drops I had added to the frontend-PS 1st-pole caps.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/26March2012_bottomfinished_1280w.jpg)
So now the only O'drops in the amps are a pair of very small values in either the frontend PS or the frontend signal circuitry that are in parallel with resistors and are not on the schematic, and they're staying there.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/27March2012_lastOdrops.jpg)
I'm still waiting for the big batch of 680uF BlackGate-Fs to arrive. Those will increase the DNA capacitance from the original 3760uF per amp (or 5440 currently, with single 680s per position) to 16320uF per amp, plus I'll use 4 per amp to bypass the main-PS caps.
-
I hope you have done a full set of measurements to before these mods so you can confirm that the amp is working the same after.
-
I hope you have done a full set of measurements to before these mods so you can confirm that the amp is working the same after.
Huh? Measurements? Not a chance. The amps work and sound great.
-
Received 50 more 680/65 BG-Ns today and got 2 pairs installed in one amp. These are bypassing the main (output-stage) supply caps.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/07April2012_2BGsmainPS_1000w.jpg)
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/07April2012_2BGsmainPS_2_1000w.jpg)
I had wrestled with buying enough to add 8 or 16 per amp and...ahem...yesterday forgot I had settled on 8 per amp and so installed just 4 in one amp. :oops:
Today I'll tackle the 2nd amp, installing 8, and probably will add 4 more in the first amp if my back doesn't hurt too much.
Thirty-two of the caps will be added to both amps' 16 DNA-cap positions which already have 16 of these BG-Ns in them. Each original DNA cap was a 470uF Nichicon (times 8 per amp = 3760uF per amp). Currently 5440uF of 680uF BG-Ns stand in those positions, and when my goodbuddy finishes his part of this project, 16320uF of BlackGate-Ns will stand in each amp...plus 1320uF in each pole (times 4) of the main PS. If I could find some higher-quality 'lytics to replace some or all of the 8 main PS caps, I would.
-
...and I've managed NOT to let the smoke out again! :thumb:
Got the pairs-per-pole BG-Ns installed in the right-channel amp, and it still works! It's astonishing how lucky I get sometimes. :D
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/08April2012_BGsmainquadtopright_1000w.jpg)
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/08April2012_BGsmainquadtopleft_1000w.jpg)
...and the bottom.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/08April2012_BGsmainquadbottom_1000w.jpg)
I LOVE how easy these things are to work on. :)
A simple way to think about all these caps here and there is to understand that each original amp had (8-times-470uF =) 3760uF of Nichicon 'lytic caps bypassing the main-PS caps. Each improved amp will have (32-times-680uF =) 21760uF of world's'-best-'lytic-caps bpassing the main-PS caps...plus MUCH-better-sounding film-type bypass caps.
Of course, if the amps didn't sound excellent originally, any and all of this 'improving' wouldn't matter much.
-
Hi Jeffrey,
As always, awesome to watch the progress. I sit in amazement. Do you know if Conrad Johnson or McCormack Audio offers any upgrades to the DNA-750's? Maybe as a way to preserve the warranty and have factory sanctioned upgrades for us, ahem, lesser qualified individuals. I never contacted them about it but I am curious.
Thanks!
Joe
-
...Do you know if Conrad Johnson or McCormack Audio offers any upgrades to the DNA-750's? ...
Joe
I understand that c-j experimented with a better-caps version of the '750 but decided not to offer it as a complete product nor upgrade. I'm sure Steve McC could and would improve them and surely better than I can--guys (like Steve, Ric Schultz, and Dan Wright) who offer this kind of service are GEAs who can hear immediately whether one change improves the sound and by how much. I can't; I just keep doing things that I 'know' will help--hence my compulsion with powersupply caps.
I'm looking more seriously for better main-PS caps; we'll see.
BTW your Premier 350SA was built with better caps--cj's 'propylene-, 'styrene-, and Teflon-film caps--and would not be much of a candidate for this kind of 'improvement'. Also, based on pictures and descriptions, the '350 would be more difficult to work on.
-
Thank you for filling in some of the blanks. I thought so.
Joe
-
I have all the 680/65 BG-Ns on hand, and my goodbuddy has begun the process of adding them to my amps. He has 6 (of 16 in both amps) single-DNA-cap postions increased to triples--here are 2 of them--
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/12April2012_2tripleBGNs_1000w.jpg)
...and will complete the rest soon. I'll get the SoniCap Platinum bypasses back on...and I might decide to add only one BG-N to each of the 2 center positions. That'd have 16,600uF (per amp) of BlackGate capacitance in the 8 DNA positions that had, originally, 3760uF of Nichicons.
I've decided to replace the main-PS caps, 8 Nichicon 12000/80s per amp, with Nichicon Muse Super Throughs, their best audio-powersupply cap. Net of the 10-piece discount, the 16 are $20.65 each, delivered. They're somewhat larger than the originals, so it'll be a little tricky to get them in--fancy that--but I expect I'll get it done. After that, I think I'll be finished. After I do this and increase the 4 center DNA-cap positions per amp to 2 and not 3 caps, total capacitance in each amp would be 93,600uF, just 6% less than the original 99,760uF and probably just right. :)
--------------------------------
...and install two BG-Ns and the Platinum bypasses I did, at least to one side of one amp.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/12April2012_1DNAsidefinished_1000w.jpg)
After Pat does the dificult work in the corners, this stuff in the middle is not bad at all. :roll:
-
...and here's the other side.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/12April2012_DNAside_10DNAsPlats_1000w.jpg)
With the on/off switch in front, there wasn't enough room on the board to stand the Platinum, so it's glued to the DNA caps.
-
The amps and the Audience aR2p-TO powerconditioner (p-con)...
http://10audio.com/audience_ar2p-to.htm
(http://i89.photobucket.com/albums/k220/jeffreybehr/Power%20concdtioners/aR2p-TOinwallfromright_1000w.jpg)
...continue to break-in and sound excellent. In fact, this is the best my system has ever sounded.
Meanwhile I've filed our taxreturns and received and begun improving a used Audience aR12 p-con for the frontend of the system.
(http://i89.photobucket.com/albums/k220/jeffreybehr/Power%20concdtioners/02May2012_installedfront_1000w.jpg)
(http://i89.photobucket.com/albums/k220/jeffreybehr/Power%20concdtioners/02May2012_installedrear_1000w.jpg)
Seems to be my year for powerconditioning.
Life is excellent. :D
-
Where do the Japanese get these names? The KG series are Nichicon's best powersupply caps and include the Gold Tune and the Super Throughs, their best. I got these from Michael Percy.
My verygoodbuddy Pat and I finally got to installing these. They're significantly larger than the originals--fancy that!--and took some headscratching (and moving one resistor to the boardbottom) to get them in. These eight (per amp) 10,000uF caps replaced eight 12,000uF caps; with the 28-per-amp 680uF Black Gate-Ns replacing eight 470uF 'DNA' caps, total capacitance is 99% of the original amount. Will be plastic-tie-wrapping them to the board soon. Used all UPOCC-copper wire to connect them--single 12g. common and double-18g. (= 15g.) for each of the + and - leads.
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/09May2012_newPScaps4_1000w.jpg)
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/09May2012_newPScaps3_1000w.jpg)
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/09May2012_newPScaps2_1000w.jpg)
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/09May2012_newPScaps1_1000w.jpg)
Knowing what I know now, this should be the first thing to do in improving the amp; then replace the DNA caps, with at least 2 680uF BG-Ns per DNA position; then add best-quality filmcap bypasses at the 4 corners of the DNA positions; then replace the frontend-supply final caps with BGs and best-quailty filmcap bypasses; and then the other OrangeDrop replacements. Live and learn.
The last step in improving these will be replacing the 8 rectifier diodes with Fairchild Stealths, which I'll do soon.
The system sounds SO good. :green:
-
Yesterday we replaced the main-PS rectifier diodes, from 25-Amp HEXFREDS to 30-Amp Fairchild Stealths. I removed the heatsinks as they were never even warm to the touch, and the new diodes, too, are hardly warm. I suppose if I were driving hundreds of Watts thru these things, the diodes would indeed require 'sinking, but I'm not, and they don't. I think I'm finished. :)
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/13May2012_Stealthdiodes_1000w.jpg)
-
One of my first amps a few years was a Sonograph 250 I bet you could have done a few things with that one.very nice amp .
-
Just out of curiosity, can you estimate the out of pocket $ you have now put into these changes (not including your time/labor)?
What would also be cool is a ranked ordering of the changes and the sonic benefit each made to the amp. I understand that may not be totally possible since a lot of these were made at the same time, or with little time between them. Just curious is all.
-
Excellent work and pictures Jeff. This is a great project. I am curious you choose the Hexfreds vs the Schottcky diodes. I found them to improve the treble but I guess they are personal preference. You are done but then again, you can still fine tune it when everything settles.
Yesterday we replaced the main-PS rectifier diodes, from 25-Amp HEXFREDS to 30-Amp Fairchild Stealths. I removed the heatsinks as they were never even warm to the touch, and the new diodes, too, are hardly warm. I suppose if I were driving hundreds of Watts thru these thing, the diodes would indeed require 'sinking, but I'm not, and they don't. I think I'm finished. :)
(http://i89.photobucket.com/albums/k220/jeffreybehr/McCormack/13May2012_Stealthdiodes_1000w.jpg)
-
I am curious why you would remove heatsinks. They can't hurt.
-
Excellent work and pictures Jeff. TYVM.
This is a great project. I am curious you choose the Hexfreds vs the Schottcky diodes. I didn't. I chose the Fairchild Stealths; c-j chose the HEXFREDS.
I found them to improve the treble but I guess they are personal preference. You are done but then again, you can still fine tune it when everything settles. Indeed.
-
I am curious why you would remove heatsinks. They can't hurt.
sts, you're correct, but (1) I had to removel the 'sinks with diodes attached to get the diodes out, (2) the Stealths are smaller than the original HEXFREDs, and (3) since the 'sinks were out, I simply chose not to reinstall them.
-
Just out of curiosity, can you estimate the out of pocket $ you have now put into these changes (not including your time/labor)?
What would also be cool is a ranked ordering of the changes and the sonic benefit each made to the amp. I understand that may not be totally possible since a lot of these were made at the same time, or with little time between them. Just curious is all.
ptm, I guess you haven't read my disclaimers about not being a Golden-Eared Audiofile. I'm not, at least in being able to characterize subtle changes resulting from single changes. I have to work hard at hearing some differences among cables, etc. I'm much better at eventually recognizing the cumulative results of several changes, so I can't rank these many different things I've done to these amps. Overall, the sounds have gotten both smoother--less edgy--and more detailed...more transparent. The slight edginess that must have been there in the upper frequencies seems completely gone now, to the point that sometimes I think the amps sound a little dark. This weekend I had to listen to one of my long-time reference recordings, Holst's The Planets*, one of EMI's great Christopher/Christopher recordings but also one that had a couple mics too close to the trumpets and trombones. When blown hard, these instruments have always sounded a bit too loud, too edgy...too hard, unattractive. Now they still sound a little too loud but never edgy or unattractive. Other long-time reference recordings also sound bess bright. But let me make one thing very clear--my system has NEVER sounded better, overall. It's very transparent, musical, easy to listen to, rich and warm when it should be but NEVER thick sounding. Only one other amp combination I've ever had--the quad of much-improved Marantz MA-24s--bettered it in any regard, that being transparency and only slightly, but those amps had little of the ease and richness that the '750s have.
I've ranked these general improvements in another thread, but if I had to start over on another pair of these, I'd do them in this order.
1. Replace the 8-per-amp 'DNA' caps with at least 16 (and as many as 24) BlackGate-N 680s, and add four 1uF SoniCap Platinum bypasses. My amps have 20-each BG-Ns. These DNA caps are in parallel with the main-PS caps but are after the 4 DC-rail fuses; the output-stage PS does not have 2 poles (other than the positive and negative halves).
2. Replace the main-PS caps with the Nichicon KG Super Throughs. Add more BG-N 680s as bypasses depending on how hard you want to work at it; my amps have 8 each.
3. Replace the frontend-PS 2nd-stage caps with BGs and add SoniCap Platinum bypasses.
4. All the other cap and other passive-parts (speaker-lead cable, input RCAs, bindingposts, etc.) replacements.
Of course some of these steps include removing the OrangeDrop caps in those positions.
I've spent somewhere around $2K for all these parts.
* Adrian Boult and the LPO; LP #ASD-3649; CD #7243 5 67749 2 6 or #CDM 7 64748 2.
-
WOW was I ever wrong for thinking they sounded short of hi-frequency energy. I listened to a couple different Rachmaninov Symphonic Dances SACDs today--Johanos's with Dallas* on an Analogue Productions 2-ch., #CAPC 34145 SA, and Jansons' with the Concertgebouw, RCO Live #RCO 05004. On both recordings, the trumpets, trombones, violins, flutes, percussion, etc., had plenty of HF energy but never sounded too bright or harsh. Both recordings sound excellent, overall, but I hadn't heard the Johanos recording for decades, and I agree with others' comments about the 'dry'-sounding hall and recording--there's just not much sound of the space around the orchestra. The system, however, sounded EXCELLENT and not lacking in anything that I noticed.
Lucky me. :green:
* the old 4-ribbon-microphone recording released decades ago on a Vox Turnabout LP, all of which were rather noisy, IIRC. This at least was on Harry Pearson's SuperDiscs list.
-
2017Nov13: Oh my...7-1/2 years later I may be buying these very amps back from the friend to whom I sold them. Would be to drive a pair of Revel Ultima Salon2s. More soon.
-----------------------------------------------
2017Nov14: I believe we'll soon have a deal and I'll end up with 'my' amps. I plan to remove ALL the old 680uF BG-Fs and end up with, in addition to the Nichicon Super Throughs initial PS caps, only the original 8-count of DNA caps. Those will be Blackgate (std.) 470/160s plus a total of 4uF of SoniCap Platinum bypasses per amp. That would leave 87,520uF of capacitance instead of the original 99,760uF. I've read this thread completely a couple times recently and am amazed at all the time and effort I and my goodbuddy Pat put in. I also can't see anything else I need to redo. :D
Because of the (temporary) low price, I ordered the same type of 2-outlet, plug-in-the-wall-outlet power conditioner, an Audience aR2p...
https://www.thecableco.com/adept-response-ar2p.html
...the standard version ($200 under RR!), for these amps. That way I won't have to replace the still-shorted-on power switches AND I'll have some noise filtering and surge protection on them.