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"Marketing cab?? Can you show me proof that DAC is marketing claims that their design is superior to the UcD? Thanks. Very HappyCheers,Robin"Maybe you missed the post that started this where the OP, a customer I believe, related what he was told by the designer....I have quoted it below for you......In any case, this horse is dead and there is no need to beat it further. Most manufacturers make such statements so it is best to just let it go for what it is.....Quote from: mfsoa on 21 Dec 2008, 06:52 pmAnd since I've already blapped more than I should I can tell you guys that he is intimately familiar with the operation of the UcD and ICE modules, and feels absolutely confidant that his designs are superior in both theory and implementation. This may not mean much coming from him if it was ad copy, but this is what I asked him point blank in person. Is it true? I don't have the tech knowledge to know, but I wanted to give you some idea of what Tommy is about and what he's shooting for here. Tommy - Hope I didn't blather too much or give away your shoe size- just giving my $0.02, FWIW.-Mike
And since I've already blapped more than I should I can tell you guys that he is intimately familiar with the operation of the UcD and ICE modules, and feels absolutely confidant that his designs are superior in both theory and implementation. This may not mean much coming from him if it was ad copy, but this is what I asked him point blank in person. Is it true? I don't have the tech knowledge to know, but I wanted to give you some idea of what Tommy is about and what he's shooting for here. Tommy - Hope I didn't blather too much or give away your shoe size- just giving my $0.02, FWIW.-Mike
Quote from: cab on 30 Jan 2009, 01:49 am"Marketing cab?? Can you show me proof that DAC is marketing claims that their design is superior to the UcD? Thanks. Very HappyCheers,Robin"Maybe you missed the post that started this where the OP, a customer I believe, related what he was told by the designer....I have quoted it below for you......In any case, this horse is dead and there is no need to beat it further. Most manufacturers make such statements so it is best to just let it go for what it is.....Quote from: mfsoa on 21 Dec 2008, 06:52 pmAnd since I've already blapped more than I should I can tell you guys that he is intimately familiar with the operation of the UcD and ICE modules, and feels absolutely confidant that his designs are superior in both theory and implementation. This may not mean much coming from him if it was ad copy, but this is what I asked him point blank in person. Is it true? I don't have the tech knowledge to know, but I wanted to give you some idea of what Tommy is about and what he's shooting for here. Tommy - Hope I didn't blather too much or give away your shoe size- just giving my $0.02, FWIW.-MikeCab (what is your real name?),Thank you for your participation in this thread. As you remarked, we starting to beat a dead horse. As for articles, press releases, patents, and the like, I figured I'd Google that for you (try the following links):http://tinyurl.com/cyxrazhttp://tinyurl.com/clu5blhttp://tinyurl.com/c39jn2Also, try the following keywords: Ravisent, ST Microsystems, Crest Audio, AudioXPress, Live Sound International, AES, Amplifier, Class-D, Digital Amp, Switching Audio Amp, Digital Recorder, EEG, EKG, Ultrasound, iPod, iTunes, Apple, Digital5, Sycom, Telefactor, Board Level Digital Amp, Module Based Digital Amp, etc.I noticed some of those who either own DAC amps or have heard them stepped in to defend our small, American, innovative company. Sorry we are not playing the game like other companies, but that's how we are able to give our customers real value instead of having them pay for a marketing program. Thanks again.WR,Tommy
Thank you for the links. I would have had better luck if I could have found your name on your web site....Best of luck....
Quote from: cab on 30 Jan 2009, 02:34 amThank you for the links. I would have had better luck if I could have found your name on your web site....Best of luck....My questions have gone unanswered, but either way, thanks again... You should really listen to one of our amps someday. We are certain that you'll be impressed!-Tommy
Well, if you don't wish to back up your statements objectively or address the EMI issues, and I understand why you would rather not, can you at least address the above issue as it concerns data that you have published?Many people prefer the euphonic "tube sound" as well, but then most people are aware that is isn't a more accurate amplification scheme, simply "agreeable" distortion. Perhaps the fact that your amp is not flat with load is much the same....
Quote from: cab on 29 Jan 2009, 09:36 pmWell, if you don't wish to back up your statements objectively or address the EMI issues, and I understand why you would rather not, can you at least address the above issue as it concerns data that you have published?Many people prefer the euphonic "tube sound" as well, but then most people are aware that is isn't a more accurate amplification scheme, simply "agreeable" distortion. Perhaps the fact that your amp is not flat with load is much the same.... I know you've brought up this issue many times before on this forum (re: switching amp output filters). A +/-1.5dB response variation at 30-50kHz is quite benign to humans. To suggest this is equivalent to the frequency response deviations of a low-feedback tube amplifier (that occur all throughout the audio band with typical speaker loads) is either disingenuous or (hopefully) simply misled. It is clear that varying design approaches lead to different trade-offs, between linear and nonlinear distortion, frequency and phase response, etc... to say that one approach is better than the other on the basis of one measured parameter is insufficient - in reality the approaches are simply different. In any case, your confrontational approach here makes me quite uneasy.
Quote from: jon_010101 on 30 Jan 2009, 03:35 amQuote from: cab on 29 Jan 2009, 09:36 pmWell, if you don't wish to back up your statements objectively or address the EMI issues, and I understand why you would rather not, can you at least address the above issue as it concerns data that you have published?Many people prefer the euphonic "tube sound" as well, but then most people are aware that is isn't a more accurate amplification scheme, simply "agreeable" distortion. Perhaps the fact that your amp is not flat with load is much the same.... I know you've brought up this issue many times before on this forum (re: switching amp output filters). A +/-1.5dB response variation at 30-50kHz is quite benign to humans. To suggest this is equivalent to the frequency response deviations of a low-feedback tube amplifier (that occur all throughout the audio band with typical speaker loads) is either disingenuous or (hopefully) simply misled. It is clear that varying design approaches lead to different trade-offs, between linear and nonlinear distortion, frequency and phase response, etc... to say that one approach is better than the other on the basis of one measured parameter is insufficient - in reality the approaches are simply different. In any case, your confrontational approach here makes me quite uneasy. Wow! What a great post. Interesting choice of words with "confrontational". Of course, as I have said many times before, the proof is in the pudding. The SOUND is all that really matters. I have had the pleasure of hearing Mike's system driven by the DAC4800A with our new non-servo modulators. I was simply blown away! The sound was out-of-body euphoric! I found myself floating in space, surrounded by the music. Amazing! A few times, I thought the amp would overload or clip, and this never happened. The Cherry has a bigger power supply than the DAC4800A, and on the bench, puts out more power and has less distortion (at high power), but this DAC4800A was just unreal in transparency and sheer power delivery. It was like discovering known tracks all over again. Unfortunately, this is when I wanted to try my new Wadia Transport with lossless recordings of my test tracks on my iPod, but I forgot that Mike didn't have a separate D/A (notice I don't use the acronym "DAC", ha ha). Anyway, as you said, audio is full of tradeoffs, and we have always leaded toward sound quality over "the specs", even though our measured performance is outstanding. We hope that people out there recognize marketing versus customer satisfaction. Our customers have said that our amps are the best the have ever heard. So, if you're worried that your speakers might load the Cherry amp to -0.5dB at 20KHz, go ahead and give it a listen. You just might be floored in the difference between something engineered to perform well on the bench as opposed to something that's engineered to sound best in your system. Thanks again, and hope to hear from you in the future.-Tommy
Wow! What a great post. Interesting choice of words with "confrontational". Of course, as I have said many times before, the proof is in the pudding. The SOUND is all that really matters. I have had the pleasure of hearing Mike's system driven by the DAC4800A with our new non-servo modulators. I was simply blown away! The sound was out-of-body euphoric! I found myself floating in space, surrounded by the music. Amazing! A few times, I thought the amp would overload or clip, and this never happened. The Cherry has a bigger power supply than the DAC4800A, and on the bench, puts out more power and has less distortion (at high power), but this DAC4800A was just unreal in transparency and sheer power delivery. It was like discovering known tracks all over again. Unfortunately, this is when I wanted to try my new Wadia Transport with lossless recordings of my test tracks on my iPod, but I forgot that Mike didn't have a separate D/A (notice I don't use the acronym "DAC", ha ha). Anyway, as you said, audio is full of tradeoffs, and we have always leaded toward sound quality over "the specs", even though our measured performance is outstanding. We hope that people out there recognize marketing versus customer satisfaction. Our customers have said that our amps are the best the have ever heard. So, if you're worried that your speakers might load the Cherry amp to -0.5dB at 20KHz, go ahead and give it a listen. You just might be floored in the difference between something engineered to perform well on the bench as opposed to something that's engineered to sound best in your system. Thanks again, and hope to hear from you in the future.-Tommy
"new non-servo modulators"I take it that the DAC4800A I tested didn't have these?What improvements do these non-servo modulators make?DanPS- In case anyone hasn't read my older posts, I tested a DAC4800A last year, and returned it under the 30 day trial period. PPS- Tommy was a much better person to deal with, than the other AC amp designer/manufacturer, who's product I tried last year.
yeah Tommy,when can i try your new the DAC4800A with our new non-servo modulators.since i love the original 4800a.lapsan
cab,The DAC amp actually does have a technical advantage over the UcD design. The DAC amp has a 3dB down point of 60kHz and the UcD amp is 3dB down at 30kHz. Because the UcD filter pole is twice as close to the audio band as DAC amp it has phase shift in the audio band in the mid and high frequencies, this is audible. The DAC amp has a filter pole far enough away from the audio band to avoid the worst of this problem,if it has a Bessel filter design it would avoid the problem entirely. The phase shift problem does not show up in a simple frequency response graph. Once again we come back to the necessity of actually listening to the amp to hear what is going on.Scotty
See link to PDF Docs with graphs of bandwidth and phase shift http://seniordesign.engr.uidaho.edu/2008_2009/audiophile/UcD_WhitePaper.pdfScotty
I think Genesis Loudspeaker is using the UcD in their new Reference Amp.And Jeff Rowland is using the ICEamp in his topend amps.Different strokes for different folks.Tommy can you email me; I tried PM but the box is full ?Rod
Quote from: jhm731 on 30 Jan 2009, 06:11 am"new non-servo modulators"I take it that the DAC4800A I tested didn't have these?What improvements do these non-servo modulators make?DanPS- In case anyone hasn't read my older posts, I tested a DAC4800A last year, and returned it under the 30 day trial period. PPS- Tommy was a much better person to deal with, than the other AC amp designer/manufacturer, who's product I tried last year.Hey, Dan. How are you these days?The non-servo boards came in just this month, so the amp you tried didn't have them.The difference is simple... The servo version uses an additional stage to compensate for DC offset. The non-servo version uses a capacitor in the signal path to block DC. The "purist" approach is not to have caps in the signal path. The low frequency roll off is less than 0.2Hz either way. We are still evaluating...Tommy
