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Below are a few recent customer reviews:

 


"Congratulations on a great product, lovely design and great build quality. "

 


"Hi Tom, just received my order this morning and im very impressed . The SDS 250 c is far superior to the Nuforce ia7 v3 that i own too.It"s a bargain for the price. It's a kick ass."

 


"Thanks Tom, My Anedio has extremely high output and I need about 5-6db less for a good match. The amp is really everything you said it would be, easily besting my ASLs in triode mode. Absolutely stunning in all regards. Kindest regards and please let me know if I can provide references."

 


"Just wanted to thank you for such an   great sounding  amp."

 


 "Tom...just wanted to let you know I'm thrilled with my 470...fabulous amp at any price...thanks!"

 


"I finally got the parts to finish the amp...sounds great with my Magnepans!!! I'll get a direct to disc playing on there in the next couple of days and I will place a comment (rave review) on your web-site!!!"

 


"I had a good listen to the Amp the last two days , for around 6 Hours and I'm very impressed with the sound . My Marantz PM11S2 I thought was very good , but the SDS 440 blow me away , everything was much better then I ever heard before , from the top to the bass amazing detailed never heard the bass so controlled and the hights so open and clear, wonderful . Have to listen a bit more and I will write a Review on your site , just  please , my english is not perfect . 

To understand where I coming from, HiFi is my hobby since 1980 and and in that time I had Mac Intosh , Audio Reserch , Theta , Accuphase ect and various Speaker , but I never had a better sound as now with your Power Amp . Before I decided to buy your Amp I was ready to buy the Marantz Power Amp SM11s1 ,AU $ 8000.00 ( everything is very expansive in Australia) I was listen too it and find not a big difference to what I had , then I searched and found your site, been reading Reviews from other Class D Amps before and found them overpriced , but decided to buy yours not because Price and Im more then happy now , thank you Tom."

 


"As you maybe remember Ive bought a good second hand Audiolab 8000P in very good condition.

Pre/pro I use is the Marantz AV7005, I use a Logitech SB with a Marantz NA7004 as DAC  inbetween some Audio Quest and Apogee cabling and an upgraded Power supply for the SB.

My current speakers are the new Wharfedale Jade 1’s with the Wharfedale stands, very good speakers but with a low 86 Spl/w and some low R issues... 

Well and now for the difference between the Audiolab and your Amp.... 

Even straight from the box it is a very big leap forward from the Audiolab, sounds like you did some tech magic wow..

Efortless power, wide and deep soundstage and the high’s and mid’s are much cleaner than the Audiolab, with a lot of details, you get wrapped in sound and the trap is that you want to turn up the volume too much

Even the low Spl of the Wharfedales is no problem at all.....

Forgot to mention that the bass is very easy to follow and goes way deeper (without any boom) than the Audiolab. 

In short, I forgot the waiting and could only say I would do it again as I know now that this is a Hi End bargain of the year 

Veryyyyy happy with the Amp, my congratulations for the design and build, you did some things outstanding."

 


"My SDS-440C amp sounds amazing!  I have been playing some Jimmy Smith FLAC files and I now hear a level of soundstage and clarity that I've never heard before.  I am just blown away by the quality of sound created by your amplifier design.  The sound reproduction is far superior to any tube gear I have used over the past twenty years." 

 


"I've been listening to my SDS 254 for a couple of weeks now, and it just seems to be getting better and better...I just wanted to say thanks for a job well done. The liquidity, the layering, the downward dynamic range, the bass...just incredible...I'm enjoying my music like never before."

 


"I've been listening to my just assembled SDS-258 for about ten hours now. Wow. The amp started settling down after a few hours and now I am really enjoying the amazing width, depth and physicality.

I found "Class D Audio" because I was looking for something that would sound as good as my recently rebuilt Stereo 70 (using a kit, a good one, from Wellborne) but not suck so many watts. I'll give a few more hours of run-in before I get critical, but I think I may have exceeded my goals. I had no idea stereo could be this good. Thanks very much for a wonderful amp."

 


"Sorry for the delay in not letting you know how amazed I am with your amplifier. The SDS-470C continues to amaze me every day I use it. It images phenomenal, and is as warm as a tube amp. It has the bass slam of the class A, with the openness and sweet sound of a tube amp. If I had not heard it with my own ears, I would not have believed it! I have both a class A amplifier and a tube amplifier. In my opinion your amp takes the best characteristics of both of them! I sent you a review on your site. If there is any forums you would like me to put down my impressions please just ask. I will post a favorable review. As I stated in my review on your site, I am still poking around the amp with a flashlight trying to find the tube! Well done Tom!! Kudos to you and your team and congratulations on making a fine product. Yes, you still can purchase product made in North America and be damned proud you did!! Feel free to quote this email to potential customers as well."

 


"Tom, I've been enjoying the SDS-470 you sent out here to Chicago, and submitted a review to the new site. In my eyes, its the perfect amplifier - it delivers more than enough power and superb clarity with any of my speakers.  I don't need to use many more adjectives than that because for me, it's all about accuracy. Now, having this amplifier poses a bit of a problem - finding worthy associated equipment.  Do you make preamps?  If not, is there anything you can recommend to pair with the SDS-470?"

 


"Tom my wife and I are sitting here listening to sketches of spain with tears in our eyes. We both applaud you and your wife for having the guts to sell such a product.!! Its that good!"

 


"If you have miles davis kinda blue play it. This is the only amp that has gotten it right!! I know because I heard the master tapes through altec tube amps and horn speakers. This amp plays it right. I don't think you realize just how good this amp is! I have been playing everything I can through it. You need to come up with a preamp to match this thing!! I am rambling. Sorry."

 


"This amp is unreal!! It is definitely top notch!! I don't get it. The thing does have the smoothness of a tube amp but the bass is tight and very well controlled."

 


"The amp arrived on Friday and I listened to it all weekend. Wonderful, flawless sound. The rock-solid bass is particularly striking and it's a real pleasure to have in my system."

 


"Happy new year. I wish you the best for you and your company. I bought a 6 ch complete amplifier (3xSDS-470) 2 months ago.

I want to tell you this is an incredible amp !! It has replaced my Nuforce MCH 300 SE (6k EU pricing) with success!!"


"Holy shit man! This amp is incredible!! Who are you really? I have been in this hobby since I was twelve( I am now sixty and can still hear past fifteen k) and have had everything from a to z and this is the first amp to get the midrange without distorting. The build was also first class. I know every name in the industry so who are you really? Tell me!"


Wow..........

Got the 6 channel amp y'all built for me from Fedex today and I am quite impressed with the build and the sonics. The SDS even prior to break-in destroys the Parasound Halo A-23 It replaces! Better control over the woofers with sweeter high-end and clarity in the critical midrange..... 
I am one happy Mastering Engineer!


 So, I finally got around to buying this amp and hooking it up. All I can say is wow! This thing sounds amazing! Just thought you'd like to know. Thanks a lot.


 These amp kits are wonderful, and crazy wonderful for the money.  As I told you I switched from a $3,000 Red Wine Audio amp, and I've never looked back.  You have a wonderful product, a great price, and fantastic service.  I wish you all the best, and have already recommended you to several people.

 


 I have tried a couple of different Preamps and your amp is very neutral.  I can hear the strengths and weaknesses of each preamp very clearly.  The bass response of this amp is nothing short of amazing.  It goes very deep and yet keeps great control over the woofers.  The highs are clean but not tizzy or tiring and the midrange is perfect, almost tube like.  In fact, if I had to summarize what I am hearing I would say it takes the best qualities of tube amps and solid state amps and mixes them together.

 


 

 I finish my two channels power amp with your CDA-258 Kit. Very addictive Sound, crisp and clear. Many Thanks. Kind Regards and thanks again for your stunning product.

 


 

Hello,

just a message to say I finished my two Dual Monaural amplifier and I never heard nothing like on my life, What is on the recording is what you hear. Background is dead quiet Best amp I've ever had including Jeff Roland, Goldmund SRM, nuforce 9 SE.

Very strong bass and nice details, very fast, and very high efficiency, my scope record 353 watts per mono power amplifier with only 1,718 Amp consumption.

This project will drive two 13 inch and two 16 inch Focal Utopia, I work on a project since six month of a pair Wilson audio speaker clone model Alexandria X2.

So thanks for all !

 


 

These amp kits are wonderful, and crazy wonderful for the money.  As I told you I switched from a $3,000 Red Wine Audio amp, and I've never looked back.  You have a wonderful product, a great price, and fantastic service.  I wish you all the best, and have already recommended you to several people.

 


I just purchased your CDA-258 KIT and am ASTONISHED with the sound quality compared to my Pass Labs Aleph 1.2 amps.

 


Tom, congrats on your SDS amps.  I just fired up your SDS-224 on the compression drivers of my high efficiency two way monitors and the performance is stunning!

 


Hey Tom,

With zero hours of burn in it blows away the 60wpc Nu Force integrated amp I was using in this system.

 It is MUCH quieter, smoother, sweeter, more detailed, more open, more transparent, more neutral, and has better time, tune, and texture. If the Nu Force is actually 60wpc then your SDS-224 has equivalent head room to a 200wpc Nu Force.

The intensity and slew rate are as good as any amp I've ever heard (and I've owned top of the line Bryston, McCormack, and Quad SS amps).

 With zero hours of burn in it blows away the 60wpc Nu Force integrated amp I was using in this system.

 It is also the quietest amp I've ever owned. The noise floor must be something like -120db or something.

 


Well I have the CDA 254L up and running, and all I can say is WOW!!!!!!!!!!!!.  It's not at all broken in, has a cheap lamp-type power cord, and I still like it better than my Red Wine Audio Sig 30.2 (which won all kind of awards when it came out).

 


This is a rock solid piece of $200 Awesomeness!

 


 

Simply stunning to listen to. I would throw this amp into the ring with anything up to $20k. I wouldn't be surprised if it beats out a $50k Gryphon amp.  


So far as listening is concerned, the lows have more headroom than the lows on my 18wpc tube amp. Keb Mo tracks, Eric Clapton's Unplugged album,  Eagle's Hell Freezes Over, Diana Krall's The Girl In The Other Room and Yo Yo Ma's Cello never sounded better.  When listening to August Rush's acoustic guitar tracks, I can feel how real the guitar tapping is and how the guitar sounds decay very well. The soundstage is superb. The highs sounded sweet to my ears. On Lars Danilesson's Salzau Music on the Water album, when playing Part 2 & Part 3 you can hear how well the instruments separate. This recording was made in Salzau Pond during a Jazz festival in 2005, so you should be able to perceive being outside hearing wind, percussion and string instruments playing all around you. The percussion instruments (scaffolding, sound rods, cutleries and steel wires) in the track's recording of Part 3 are placed in such a way that you hear them clinking from left to right. There are instances when these percussive instruments disappear into the background so ever slightly until they just disappear, and the amp rendered it effortlessly and to my ears never sounded harsh, musshied (if it's the right word) and cramped. http://www.amazon.co.uk/Salzau-Music-Water-Lars-Danielsson/dp/B000FQJO56 

 


 

This build went brutally...as in brutally EASY.   The hardest part is in the details, IE where to mount things, picking wire, etc.   It's up and running.   Without listening critically it sounds great, and powerful.   Right now it's pushing some vintage RTR 280 DR's which are pretty power hungry, with ease.  I  can't wait to build another one.

 


Now on to my first impressions.  . .

When I first started listening, I did notice a few things.  I thought maybe they were simply due to the fact the music I had going on had not been played for a very, very long time. . . and had not been played at all yet on my current set-up (minus the Class Ds).  This was the remastered Dark Side of the Moon (the redbook version burned to my PC from the SACD/redbook that came out a few years ago).  Well, what I heard was. . .simply more detail!  However, some things sounded quite harsh at some points (such as the heavy tremolo on the electric guitar on Money).  I think I've noticed this before. . .and I think it may have been because I was probably ever so slowing increasing the volume. . . and may have been a bit too much for my monitors?  I'll try it again later.  This was also early on and I was paying much less attention to the music overall as I found myself doing throughout the day. I haven't had a similar annoyance since, so I would say it was the material and/or speakers as the culprit.  As I said, I'll try it again later.

Anyways, due to the fact I hadn't heard this material in awhile and on this set-up, I put on some stuff I have recently listened to:  Pink Floyd - The Division Bell; Wilco - Kicking Television; Wilco - A Ghost is Born.  David Gilmour - Live in Gdansk. With everything, definitely have noticed better defined bass.  I have also (again) just noticed simply more detail/definition.  On The Division Bell, I remember noticing a bass line (forgot which song) I remember having that deeper EQ (intentional) sound to having a that same sound, but with a subtle "string" tone to them.  I was pretty amazed I never really heard that before. :o  Could all this be due to a quieter background?  Maybe/possibly?  I don't really care. . .all that matters is I like it so far!  (By the way, that Gilmour album (triple CD, 2 DVD version) simply sounds fantastic  :bowdown:)

Yeah, I don't think the harshness is related to the amps.  I posted in that post, or the next one, that I attribute that to the material (unlikely), or just pushing the monitors too hard.  Also, It was early on in the impromptu listening session and I was not fully focused on the music.

I've been extremely impressed so far.  VERY nice, Tom!  Thanks for a fantastic amp!

So far, I've been stunned by the details I'm hearing for the first time. . . amazing.

 


 

Well I spent quite a bit of time last night listening and tweaking cables. I was originally using DIY silver cables on the 120 amp and from the preamp to the crossover. Things were sounding just a tad too bright so I went back to all copper blue jeans cables and things seemed a bit too rolled off. So I left the BlueJeans on the amps but ran and old set of shielded Clarity Labs cables that are silver coated copper from the preamp to the crossover. 

Voila. Everything came into place and I had the right balance of high end extension (IMO) in the mix. Also, I had mentioned that the new 250 board was quieter than the 120? When I pulled the unshielded silvers out of the 120 amp, they are now both dead quiet, ear to the speaker. I still can't believe what that does to bring out low level detail compared to my tube amps. 

So overall, this is the best my system has sounded, period. It is balanced now and sounds equally good with digital or vinyl. I don't know if I've ever had this kind of equilibrium in my system before. Biamping has always been a bit of a challenge for me with compromises but I think I've found the solution. Thanks again Tom for you excellent products, great design "ear" and most of all above and beyond service.

 


The module certainly plays music.And it does in a way i Hadn't heard before. Clean sound,accurate,very crisp,detailed. For many years i listened to English amps. A bit sweet,round edges,more musical as they say.But the class D combined with my new tube preamp is a perfect match. The sweetness of the tube with the accuracy and speed of class D gives me a very well balanced and musical sound. It certainly paid off. The second module is not necessary. The pre amp output is high enough and the speakers quit sensitive (91 dB) so I dont't really need extra power.

 


 

Gawd, this amp has jaw dropping sound!   I understand the excitement now. Many thanks

 


 

I am VERY pleasantly surprised as to how much better the amp is, I was hoping that it would just sound as good as the 60 watt original with large power supply that I was using. It has totally surpassed my expectations and then some. I now think your statement of placing the SuperD up against anything is completely valid, you have knocked it out of the park on this one. It seems to have settled in nicely after only several hours of breakin. 

I am still using my HK as a pre and I only have $1200 diy speakers but I now feel like I have a world class system. My wifes comment was it sounds better than live because its so enveloping, and that comes off the heels of praising the first one. I think its control over the music is uncanny, I felt the first amp had a tight sound compared to my HK but I can say it again, the SuperD has a tight sound compared to the original.

 


 

You have got a real winner here. It just clearly has a better handle on the music. I don’t know what portion of my results can be attributed to increase in power but I have better tighter bass and great detail and separation.  Its just much tighter sound all the way around. I sold my first amp in the first 10min so I can’t compare but I am most certain I could never go back. I am gonna give some more time but it pretty much night and day. 

I am very pleased!

 


 

Thank you for the wonderful amp. It produces tube-like sound, warm and detail. It has the dynamic and pace. The bass is very clean and tight. I also heard nuances that I have never heard before. I guess it will get even better after run-in. 

 


 not supprisingly the amps came together slower than expected.  Last week I then made the rookie mistake of plugging them in before they we're fully complete.  They sounded great, so of course I couldn't unplug them to finish construction.  Well I finally got them unplugged long enough to complete them.  I thought I would drop you a line and thank you for all your help answering my questions.  The amps sound incredible, detailed and smooth.  Similar to some others that I've heard, except your amp seems to have a much more dynamic bottom end.  

 


 

The amp arrived today thank you.  I don't know how you got it here so fast, but I am amazed at how quickly it arrived.

In any case, it was a cinch to hook up. The most time consuming part was actually mounting it to the board. In any case it was really easy. Now the good part. I really like how it sounds with the Dynaudios.

Just on first listen I can hear that it has great potential. Cant wait till it settles in. Also I hooked it up with generic wire, RCA's and binding posts for testing purposes. It definitely warrants the good stuff, and that will be my project when I return from my work trip. 

In any case thank you. I really appreciate a great product for a terrific price.

 


 

Hi Tom,

Well the verdict is in on this comparison. Three of us "critically" compared your amp with the W4S STI-500 yesterday. We listened to the WFS on its own, then used the Class D with the WFS preamp and then ran the ClassD with Kent's Dodd Audio tube pre. I was polite and circumspect in this review on Acircle but honestly we all agreed, your amp shredded the W4S. No comparison whatsover.

 


 

Got it going!!  Unbelievable sound.  I am sold.  I will definitely be ordering more soon.  Thanks for all of your help!!

 


 

This amp is truly amazing!  It's got that analog warmth to it that my other digital Class D rack amp doesn't have. And you were right, it runs dead quiet.

 


 

We were happy with our gainclones until we tried your amp.  Right out of the box I wasn't impressed with the first one we tried, but Trung brought it back to my house last Thursday and it was amazing.  In fact, when he left and I re-connected my gainclone - it just didn't work for me anymore...  That amp had been played for probably 300 hours at another friends house. 

The high end detail is amazing, the midrange is tube like, and the bass is tight.  Really a top notch amp.  

 


 

My buddy brought the 250w x2 amp back over to my house again last night - WOW!  What a difference from the first few minutes that I heard it... everything about the amp is amazing.  The high end detail is freakishly good!!!  I now understand why people would sell there big dollar amps for yours. 

I have been to the RMAF show in Denver a few times and have seen and listened to a lot of high dollar gear, and your amp rates with the best!


Got it going!!  Unbelievable sound.  I am sold.  I will definitely be ordering more soon.  Thanks for all of your help!!


I had several friends over last night who were greatly impressed by the sound. I suspect they'll be buying an amp to try it. I also have another friend who just got a pair of Bel Canto 1000W Monoblocks on loan yesterday. We both agree they sucked compared to your amp. I's talking about trying your 500 wpc amp. Later, I'll post a review on your site.

Thanks again for all your help. You have a great product.


Catherine & I continue to enjoy the system I built using your amps :-)    I have had a few friends listen to the system, and have had many accolades. 

One fellow who's a professional musician sat in silence and had tears in his eyes---No Kidding !

 I have been looking at class D for quite a while as the technology has matured in the past year or so to the point that it rivals other forms of amplification. I was talking to a company in Holland ,but they seem to have stopped communication and were quite pricey, so I dropped the whole idea for a while until I happened onto www.classDaudio.com by chance. I spoke to the fellow who runs the business, and was impressed by his openness and knowledge of the subject. I also liked the build quality ( all built in the USA ) and the price was more that reasonable! He supplies the transformers, power supplies, and amps. The transformers are toroidal as you can see in the pictures I sent, so are very efficient and little to no radiation due to the toroidal design. The system has come to life and the speakers are singing the praise of these amps !  The attack of brass cymbals is right on as well as vocals and guitar. I also checked out a few piano cuts looking for the harmonics and having worked in a station that had a full studio ,as well as my experience monitoring a full surround recording of Oscar Peterson in Toronto, and attending many professional audio conferences, I can vouch for the audio quality !


 Tom,
Just wanted to thank you for such a great amp, I putted it together this weekend and I couldn’t believe that even without proper cabling and shielding it sounded amazing.


just wanted to say that I am very impressed with your product! dual 500 watt monoblocks out of such a small package, I couldn't believe my ears! I currently have them hooked up to a pair of 600w peavey's and the output is very impressive. thanks for a great product.


Well Guys... 
I just finished putting together my 120W X 2 240W X 1 CLASS D power amp...that drives my big 15 inch speakers. The amp comes assembled...American made...The amp may be small...but it's a powerhouse...hard to believe that much power could come from such a small package...outstanding sound...


We noticed your Class D amp on eBay, and when I discovered what you were trying to do for our country, I immediately ordered the kit in the hopes that we might OEM your amp and thereby support your important social efforts.

We set up an A/B test between your amp run in stereo against a tweaked, commercially available version of an ICEpower amp.

Because I recently spent 2 years on a team at A/R-Audiovox trying to develop a forward thinking Receiver, I know for certain that the ICEPower stuff (at least 1.5 years ago) was the ONLY game in town for a lot of reasons, the first one being sound quality.

The listeners were 3 trained, experienced, and terribly jaded/critical judges of very high end sound.

Your amp fared very, very well in the comparison tests btween it and the ICEPower (which was in balanced config!!) and also between it and a very high quality ADCOM amp. The target loudspeakers were Earthworks StudioReference speakers.

We feel that the amp could make a very viable High End Power Amplifier. 


I really like it...lots of power...with no discernable distortion...and so clean...no hum...and drives the socks off my big 15 inch woofers!


Tom,

      A finally got time to get my class d amp together today and it sounds great, I can't believe the sound it has. I have built several amplifiers and been arround amps and have several that I have collected through the years. All kinds ,solid state , tube , all classes, repaired all kinds and I have not heard any that sound any better than this thing. It's so clean and detailed it will steal the pants off lots of expensive high end equipment. So clean it brought the flaws out in my preamp.

Harry