Class-D amps - a different re view

Atmasphere, Thank you for your contributions to this thread. I was discussing this thread with a friend a few days ago. We both agreed how much we appreciate your contributions and how you participate with a constant high level of courtesy and professionalism. You set a standard we should all strive for.

Ar-t - I have the smallest of the series and 23.5V on terminals. To deliver 5x more power they need voltage around 52.5V. I think it stays below safe level of 60V but agree with you that this might be of concern. I don't touch speaker connectors but with largest unit I would be concern about toddlers. Hypex is free from it.

As far as I know filter set at 65kHz has couple of chokes on one toroid (common mode chokes) and ouput capacitors. Frequency of this is in general fixed execept when Q is changing. Mine is listed at 65kHz at 8Ohm and 45kHz at 4 Ohm. Speaker impedance changes will affect frequency but it happens (if I remember) usually in lower frequency range. B&O lists idle frequency 400kHz-460kHz but for operating frequency they show 0-460kHz. I don't know what they mean - it cannot certainly be in audible range. Maybe they include audio signal in the spectrum?
So - there are some changes in the carrier frequency and therfore its attenuation. Audioband should have some phase shift - about 20 deg. increase at 20kHz compare to 1kHz. Is it common?

There is something different about highs of Icepower (might like it or not). Is it caused by limited bandwidth or dropping damping factor?

Some people called midrange of Rowlands 201 being magic and almost everybody likes bass performance but highs sound different.

There is no easy choice in design of amps. Class A has about 1/8 of efficiency and large power units are costly if not impossible. Class AB have nonlinear element in the output and require modesty in design. General problem is setting negative feddback to deep to get specs. THD for instance is difficult to hear below 1% but I would not buy class AB amp with 0.001% THD or very High DF. Sane designer would use the most linear elements setting bias current really high and would bring down thd only below 1% and then would limit input bandwidth to one amp had before feedback to prevent TIM. Unfortunately companies are racing for best specifications. I would advise to take specifications, promtly discart them and just listen.

Class D bypasses many problems and I know this is just begining. Comparing them to traditional amps is fair when is done to units in the same price range.

Unfortunately companies are racing for best specifications. I would advise to take specifications, promtly discart[sic] them and just listen.

Still the best advice anyone can give.

"Unfortunately companies are racing for best specifications. I would advise to take specifications, promtly discart[sic] them and just listen."

Hmmmmm.. these stupid people from Spectron wrote on their silly web site:

" BLA BLA BLA
BLA BLA BLA
YADDA, YADDA, YADDA,
BLA, BLA, BLA
BLA BLA BLA
YADDA, YADDA, YADDA,
BLA, BLA, BLA
BLA BLA BLA
Conclusion: We hear time and time again that the numbers on the data sheet do not predict an amplifier's sound quality. While largely true in the past, today more and more parameters, measured correctly and even more importantly - truthfully reported - do reflect well some very important amplifier sonic characteristics. When you are considering buying any amplifier, the first question must be if it can drive your speakers at all. If it can drive your speakers, then can it drive them well. Can it drive them, at the very least, without euphonic coloration, muted treble and veil etc? The right approach is to check the amplifier's distortion level and output impedance at high frequencies(* - for class D specifically - my comment here) . Also look for peak current and its duration, flatness of frequency response, noise level, bandwidth etc. Of course, Spectron also considers the speed of the feedback loop and inclusion of the output filter in the feedback loop to be of great importance, even if an audiophile cannot really check on this. Each and every one of these measurements contributes to a gorgeous musical experience, and each deficiency will be readily apparent to the critical listener."

We have concentrated on the Rowland 201 because the most vociferous defender of class D happens to own that Rowland. I have not heard any of the Rowlands, and have no opinion of their sound.

The builder of my amps, the H2O (a 500A module amp), also makes the digital power supply amps. He makes no bones about it, he feels the 500A module, mated to his massive power supply, sounds better.

The point of this is there are a large number of class D amps. One cannot draw a general opinion through these amps, unless that opinion is derived from a built in love for tubes or solid state sound.

For my ears, Class D amp builders are not trying to achieve a sound like tubes or solid state. They are trying to amplify the truest signal to their ability. If it were the mimicry of tubes they were striving for, they would not have employed a passive filter to peel away the manufactured even and 2nd order harmonics, the very distortion that endears some tube defenders.

Recently I auditioned a higher order DAC. It introduced a lot more tubes into the mix. While the huge DAC did spit shine shine separation, and power, it's three more tubes obviously lent a good deal of color.

My preference, and I must insist it is my preference, is for less coloring, and more raw truth. My amps and preamp (class A) are doing that for me.