[john dozier]

Both of us have sota systems and find the ClassD to be so transparent that even small changes in the rest of the system are clearaly audible.. Regards

[matt_garman]

FYI, the US warehouse (based in Oregon) of Hifimediy now stocks Connexlectronic SMPS's.

That's really interesting!

I've mentioned being extremely impressed with the Connex earlier in this thread. So if your power demands fit I highly recommend them, especiallyas they are only 4x4 and weigh nothing compared to the toroid and cap bank that comes stock with CDA amps

Just some notes on my experience with this, for anyone who's interested.

I have two SDS-470 amps, one was completely done by Tom/Class D Audio, i.e. shipped in fully finished & working condition.  The other is a DIY that I put together myself (although in a case from Class D Audio, so it looks like a pre-built one).

The DIY version uses the Connex SMPS800R power supply (actually recommended by Tom when I asked him what switch-mode PSU I should use).  My DIY version also supports only XLR inputs, and I didn't use the gain pots, but opted for fixed resistors (not those fancy/expensive metal film resistors mentioned earlier in this thread, but cheapies from Mouser).  To me the DIY amp sounds a little better than the stock.  But I haven't done a true blind A-B test, and in fact, I suspect if put to the test, I wouldn't be able to tell the difference.  But there is some non-tangible benefit to running a DIY rig. 

Downsides to the Connex SMPS: my original goal was to have a very small, lightweight but high power amp.  I tried putting the SMPS and SDS-470 in a case that was just big enough for the two boards.  That resulted in overheating issues (my experiences are documented somewhere in this thread actually).  Tom was super helpful through all this.  Ultimately, though, my conclusion was that the SMPS800R puts off some heat, and a larger, better-ventilated case is necessary.  I've since replaced that case with the "official" Class D Audio chassis (which really isn't that big), and haven't had any heat problems.

If I had the time (and was more motivated) I might try to revisit the small case setup, but this time with a slow-running (i.e. silent) fan.  Note also that the SDS-470 is the highest powered Class D Audio amp, and the SMPS800R is one of the highest-power Connex SMPS modules, so going with lower power components might be all that I need.

One other small nit with the Connex SMPS: it makes a whining sound when there is no load, i.e. when there is no music playing.  It's a pretty quiet whining sound (my wife can't hear it unless she's physically close to the amp and I point it out to her).  And it goes away when playing music anyway.  I asked Christi (the "Tom" of Connex) about this on the DIY Audio forum, and he said it's to be expected (he explained why it's so, but the technicalities were over my head).

I believe that both Tom at Class D Audio and Christi at Connex are continually revising and tweaking their boards.  It's possible that a newer version of the SMPS may not whine.  It's also possible that either (or both) boards have had their efficiency increased and/or heat-sinking improved.

[bruson2]

Not very expensive Niobium Oxide Caps from Digikey http://www.digikey.com/product-search/en/capacitors/niobium-oxide-capacitors/131747

I use a Connex smps with my sds 258 amp. They sound great together.

For another project I'm going to try a Sure amp board off ebay using the IRS2092.
http://www.ebay.com/sch/m.html?_nkw=&_armrs=1&_from=&_ssn=sure-hifi&rt=nc

[john dozier]

Niobium caps are not expensive, just great SQ. State of the art material and construction-more expensive does not always mean better SQ-it depends on the application. Regards

[benh]

I am looking at the SMPS 500 (http://us.hifimediy.com/index.php?route=product/product&product_id=72) as a PS for an SDS 254 amp.

That power supply has 500 watts continuous and 650 watts peak power available.

My sense is that given an input voltage range of 40-50vdc for the amp board, output from the PS of 45vdc is a solid choice.

Given that peak output power of the SDS 254 is 500 watts, I'm curious as to if this power supply has enough power available if I have sustained 500 watt demand.  I don't actually expect that kind of demand, but would prefer to buy a slightly beefier PS if necessary and avoid the issue entirely.

Seems like it will, but want to confirm before I pull the trigger.

[wgscott]

Well, it has been a couple of years since I built my Class D amp. I have an SDS 254 kit with two amp boards (passively bi-amping at the moment, hope one day to actively do it).  I am still quite happy with it.  Currently, it is housed in an empty Peachtree Audio Nova-type box with custom front and back plates.  I use my Nova now as a DAC and pre-amp.





For awhile I tried a NAD C390DD direct digital amp. It has great clarity and a dead silent background. However, when I returned to my Class D amp, I realized I was missing quite a bit in the way of dynamics.  I'm not sure if this is just because mine had more power, or if there really is something about Class D audio class D amps vs. the class D DAC/amp configuration and power supply NAD has.

It does make me wonder if I should try a NAD M51 DD DAC/digital pre-amp with the Class D Audio amp.  Any suggestions?

Also, has anyone directly compared Class D audio amps to Hypex Ncore nc400?

[Nick77]

         Also, has anyone directly compared Class D audio amps to Hypex Ncore nc400?                                                                               

I got too, the Ncore was clearly a step up in overall resolution and dynamics, bass is a stand out. But i slightly preferred the more musical ClassD amp in my audition. My ClassD amp is a premium build with 60k Panasonic capacitance. The Ncore was a baseline build, I believe had it been built with premium parts it would have killed the ClassD. Hope to upgrade someday, but the ClassD is a great performer.

[k6davis]

It does make me wonder if I should try a NAD M51 DD DAC/digital pre-amp with the Class D Audio amp.  Any suggestions?

I've been running an NAD M51 balanced into a stock Class D SDS-470C into Magnepan 1.7's for over a year now and the sound is fantastic. The NAD & Class D are great individually and they compliment each other well.

I can't believe I'm getting sound like this from such a modestly priced amp. I was prepared to spend more (and have in the past) but I've never had sound this good before.

[krikor]

Well, it has been a couple of years since I built my Class D amp. I have an SDS 254 kit with two amp boards (passively bi-amping at the moment, hope one day to actively do it).  I am still quite happy with it.  Currently, it is housed in an empty Peachtree Audio Nova-type box with custom front and back plates.  I use my Nova now as a DAC and pre-amp.

Nice enclosure! I really like that look... so where do you get empty Peachtree Audio Nova-type boxes? Was that from a unit that went kaput?

[wgscott]

They sold me an extra.  I told them what I wanted to do, and they were kind enough to do it.

Now they sell their own Class D amp.  I wonder if I planted a seed ... ?

[wgscott]

Would I benefit from putting the toroid and the power supply board in a separate, metal enclosure, perhaps directly behind the current box which would continue to house the two amp modules?  Right now everything is really crammed in there.  I do hear a faint amount of hiss when nothing is playing, if my ear is within say 6" of the speakers.  It is no big deal, but I wouldn't mind getting rid of it.  Also, when I turn it on, I get two pops, presumably one per amp board. Is there a way to prevent that?  When I have only one amp board connected, I don't get any pops.

[maxitonus]

I just have recently even further improved the sound of my system using one SDS470 amp connected to Duntech Prince speakers.
The sound is as good as with a DEVIALET D Premier amp, costing about 12000Euros..I am not even interested into listening to the N-CORE in comparison since the sound i get is (according to my own opinion) really close to the ideal..

The essential improvements /tweaks of the SDS are concerning the Linear Power Supply and the cables, NOTABLY the Mains power cable to which the amp is extremely sensible.And the interconnects and loudspeaker cables.=

-switching to 6X Panasonic caps (60kMuF instead of 28.2kMuF)is better but not sufficient, i added 2X3 1800MuF panasonic caps at the amp board input, aiming at decreasing further the internal resistance of the PS.The result is good, the amp becomes "imperial" means seems to operate with more "ease".
-The Mains power cable is of great importance, notably for the extreme treble,which can be understood when looking at the current impulses entering the PS, which need fast transitories to be conveyed by the cable.I copied the principle of Shunyata by making a cable with 4 standsX(12X0,28 litz wire) but 2 strands are turning clockwise and two counterclockwise in order to reduce the cable inductance.This cable helps for the high frequencies,("air")
-i think the pots must be conserved since allow to tweak the slight difference of channel sensitivity, BUT the pot's wires must be shortened to 4cm instead of about 25 , i located the pots below the XLR inputs, by removing the RCA plugs as well as the (useless) switch for my own case.(removing useless wires brought an improvement in purity by decreasing the useless cable capacitance)
-the loudspeaker internal wires are of bad quality, i replaced by good ones, silver plated and litz.

NOW, about the interconnects and speaker wires:
-use UNSHIELDED interconnects seems to me a must.
-reduce the section of cables going to the woofers since the natural tendency of this amp is to give a little too much "high-lows"
-use litz wires for the treble in order to "purify" the sound and help for the extreme treble
Some hesitation and tests will lead at the end to clearly improved balanced results,if patience is used....

The shortcoming of this amp is to be extremely sensible to its environment, which leads to anticipating that if the user is not ready to tune it slowly and correctly with the system's remainder,the final result can be a lot lower than the maximum
 attainable.

[Nick77]

     i added 2X3 1800MuF panasonic caps at the amp board input,                                                                                 

Can you please add more detail on this mod. Are you referring to the 4 large caps next to the heat sink? What was their value before switching to pannys? What panasonic cap "FC"??

I also have 60uf on PS and very interested in your board mod. 

[maxitonus]

3 FC panasonic caps of 1800MuF each, in parallel, are connected between de (+) and the earth input screw











 pins, 3 other ones between the earth and the (-) pins.The mod is very simple to complete,one hour work is really a maximum.

[justd]

Can i use the SDS-470 rated at 300watt@8ohms and 600watts@4ohms to drive mirage OMD 15 (nominal 6ohm, and minimum 4ohm) rated at 25-250watts. Or will these blow them up.

[matt_garman]

Can i use the SDS-470 rated at 300watt@8ohms and 600watts@4ohms to drive mirage OMD 15 (nominal 6ohm, and minimum 4ohm) rated at 25-250watts. Or will these blow them up.

I use that exact same amp with my 4-Ohm Salk Songtowers, with similar power ratings.  I haven't blown them up yet.  I believe it's possible that I could destroy the speakers if I tried... but I'd have to go out of my way to do that, including torturing myself with ridiculously loud volume.

The extra amp power is nice for dynamics in your source material.  We're talking very brief peaks of power draw.  If your typical listening levels are obscenely loud, I suppose those dynamic peaks could conceivably get into the danger zone for your drivers and possibly harm them.  But I'm willing to bet that such a listening level would be quite unpleasant (unless you happen to live in a sports arena ).

[justd]

Thanks Matt,

I already have a pair of CDA 254s and a CDA 224. I am using them as a 5 channel amp in my home theatre. The problem is that in case of some brief highs, the amp is clipping. Also i feel that the rear surrounds are not as loud as they should be. Thirdly, to get to the desired level of volume i have to often go to 65 on my emotive UMC-1 ( max volume is eighty). earlier it was loud enough at 50 or 55. So i don't know, if that is the problem with UMC-1 itself.

I am thinking of migrating entirely to three SDS-470 for the five channels and go for the Connex power supplies. Thanks again for the insight.

[tushma]

Hello to alls!!! Im from Croatia and im new in DIY, but i have nice friends who are monst...masters in that so im not scared of answers! The question is what classDamp + preamp fits for my quads 11L, 86db speakers? Music is....... everything except classic (for now), and budget is 400-500$! Any suggestion is welcome! Thnx in advance!

[I.Greyhound Fan]

I would run this kit and a Grant Fidelity DAC-11 preamp.  I run this combo with my Magnepan MMg's in my second system and it sounds great.   The stock tube in the Grant is not that good.  I run an early 1960's telefunken 6DJ8 or a 1960 Amprex non aframe with the halo getter.

http://classdaudio.com/amplifier-kits/cda-254l-kit.html


http://shop.grantfidelity.com/Grant-Fidelity-TubeDAC-11-D-A-Converter.html

[tushma]

Thnx a lot!!! it looks very promissing, i hope it only would not be overkill for my quads, cause they are spec. with max 130wat!!