Oh how I wish Class D amps ...

One thing to be careful about is reliance on simple measurements such as frequency response, or THD.

Ideally, a measurement such as EVM that is used in the wireless industry would be a more appropriate measure of the quality of the amplifier.

One example of the problem with measurements like THD is that its easy to crank up the amount of feedback to create good THD measurements. However that will smudge out the transients in a signal and cause a dull lifeless sound. That is why on Class A/AB designs the better sounding amps tend to be the ones with zero global feedback.

Going back to Class D designs, my experience with several ICE amplifiers has been they tend to distort the transients - particularly the quieter signal levels. Perhaps this is due to the deadband issue that is described on the Mark Levinson website - I don't know. Its a type of digital nonlinear effect and so can't be described by simple 2nd order/3rd order products.

I recently got a Spectron digital amp, and haven't noticed this issue at all so far, although I have been using it in balanced mode, which perhaps serves to reduce the effect to the point of not being noticeable.

I am also intrigued by the idea of the Devialet amp - which combines class A with a class D to capture accurate transients - although I have yet to hear one.

I think I have been more than patient with ICE amps, including changing around my interconnects, power cables, speaker cables, even preamps to get the ICE amps to sound better! And tried several ICE amps to boot!

Don't get me wrong - the detail was not poor by any means - it was fairly good overall - but somehow there was something missing on higher frequency transients that created an ever-so-slight digital, plasticky sound.
When I did a comparison between the state-of-the art latest Ice amp (Bel Canto 500m) and a 8 year old Sim Audio Class A/AB amp with zero global feed back - there was simply no contest. Especially at low volume levels I found the Bel Canto would compress and sound anything but audiophile, whereas the SimAudio operating in Class A mode managed to retain most of its nuances, just at quieter levels.

I honestly don't know what else I could have done to bring out the best in the ICE amps. . . if you have a special recipe I sure would be interested to know! :)

As far as the low input impedance I thought this was mainly true with older Class D amps? For example all the recent Bel Canto and Wyred amps advertise that they change the ICE input circuitry to accomodate a wider range of input impedances. Do you think this is still an issue?

I do agree with the power cable suggestion though. The Class D amps do seem to improve significantly when you clean up the EMI. I used a Signature Lessloss cord for this - it really brings the sound into focus. I found other components could make improvements - but similar in nature to how they would make improvements on a Class A/AB amp.

I still think the sound of the BC 500m seems lacking but perhaps its a question of power - I have low impedance speakers with a long run of speaker cable - so perhaps that was the issue. But then again I had tried them out on my older system that had high impedance speakers with very short cable runs and they definitely didn't sound as good as the Simaudio amp. At high volumes it was close, but at low volumes the Simaudio managed to stay very musical but the BC just compressed badly.

Since then I have switched to the Spectron - was not able to compare it against the older system/Simaudio, but so far from memory it provides a very similar sound to the Simaudio, but with more cleaneliness - so I am very satisfied so far.