Class-D amps - a different re view


Martin Colloms, the editor of HiFi Critic (ad-free mag from the UK) have recently published the review of several different Class-D amps, together with an in depth technical analysys and measurments.

His conclusions were not favourable, to say at least:

"I regret that not a single model merits unqualified recommendation. Price is not the issue; the poor listening tests speak for themselves. (...)
At present we have to take the prudent view that good sound might be possible from switching amps, but we haven't heard it yet."

BelCanto REF1000 (ICEpower) - score 10.5 pooints
"The ICE power module used has a dependable reputation, and the design is well built and finished as a whole. While I would not suggest that you shouldn't try this amp, on sound quality grounds alone I cannot recommend it for audiophile use."

Channel Islands D100 (UcD) - score 13 pooints
"While I have reservations about a number of aspects of sound quality, and advise personal audition, given the solid lab results (...) the overall performance and the moderate price, these CA Audio monos do make it to the 'worth considering' cathegory."

NuForce 8.5V2 (proprietary technology) - score 9 pooints
"Yes, the price is good for the power output. Yes it's pretty, light, small and runs cool. However, the sound quality simply does not justify recommendation." (on top of that the NuForce amp measured very poorly - Elb)

Pro-Ject Amp Box (Flying Mole) - score 5 points
"I'm sorry to say that Project (...) was a real disappointment in the listening tests, and can't be recommended."

Just as a point of reference, recently reviewed Krell 700CX scored 100 points, CJ Premier 350 - 110 points and ARC Ref 110 - 135 points.

At least someone have had the balls to say it. This is why HiFi Critic is THE mag to subscribe.
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Atmasphere...Since the output devices are simply ON/OFF switches, I see no point in using tubes here. The supposedly superior linear amplification characteristics of tubes would not be relevant. At the input, a tube could be used, but why not put it in the preamp.
Eldartford, I agree, unless you consider that commutation issues often limit semiconductor switching. A tube can switch at very high frequencies. Of course the idea is pie in the sky, but the point is that the technology is still unfolding and we really don't know yet where it will go.

Although the ICE module is one of the better sounding modules right now, the technology is changing so quickly that if you are 6 months behind, its already old hat.
Atmasphere, Although the tube guys will never admit it, class D ICE has already eclipsed their performance in real world terms. Never will class D emulate the fantasyland of tube amps.

A nice The nice thing about ICE you can set it's tempo with tubes. My driving tubes are in my DAC. You'd be surprised how close class D can get to the romance of tubes by running tube signals through them.
Muralman1...You said "Never will class D emulate the fantasyland of tube amps" but I suggest that your descriptions of your H2O amp come darned close :-)
Atmasphere...When transponders (radar response avionics for planes) were first introduced they were all transistorized except for the output device which was a traveling wave tube. The high RF frequency used by the transponder was cited as the reason for the TWT. The TWT was a frequent failure item. Thank God it has now been universally replaced by transistors.

The switching frequency of digital audio amps is well below 2 MHz, and solid state power devices have no problem at such frequency. My CI D200s (UcD) switch at around 400 KHz and my CarverPro ZR1600s (TriPath) are up to about 1.5 MHz.

I wish I could afford one of your OTL amps, which I believe exploit the benefits of tubes without their drawbacks (except cost).
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