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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.
128x128elberoth2
atmasphere's avatar
atmasphere
11,954 posts
 
Muralman1, I've not checked out all the modules that are out there, and I was careful to comment to that effect.

FWIW though, distortion has nothing to do with what impedances an amplifier will drive. The two issues are unrelated. Neither is THD a good indicator of how an amplifier will sound. The current test and measurement paradigm does not generate specifications that are intended to let us know how an amplifier might perform sonically.
eldartford
4,262 posts
 
Atmasphere...I agree that the specs we measure are intended to verify that a unit is performing as per its design (ain't broken) and do not necessarily correlate with sonic quality. (Although high IM distortion is very anoying to me). However, if the ideal amplifier is a "straight wire with gain" why don't we just compare the output, adjusted for gain, with the input while playing some complex waveform like music, and over a range of amplitudes. "Total Error" would be the parameter...who cares if it's harmonic,IM, or noise. I submit that many SS amps would score well, and many tube amps not. However the tube amp fans would say that the ideal amp is not a straight wire with gain, but rather is a harmonic synthesizer, with gain. To each his own.
elberoth2's avatar
elberoth2 OP
1,223 posts
 
Eldartford - the fact is, that some distortions are more easily accepted by human ear than the others. That is where tube designs have their advantage. They may measure as good (or as bad - depending on the point of view) as the SS design, but in the most cases, they will sound much natural to human ear.
guidocorona
4,298 posts
 
What can I say, sadly, I am probably not a member of the species 'Homo sapiens', because 'tubey' distortion do not sound at all priviledged to these poor ears. [chuckles!] Oh well, guess there are worse things in life!
atmasphere's avatar
atmasphere
11,954 posts
 
Guidocorona, you may not believe this but I agree with you- I don't like 'tube' colorations either. I think many of those colorations have to do with design considerations rather than the tubes themselves.

Consider that because you have heard some tube amps which have coloration does not mean that all of them are like that.

I don't really like *any* colorations (tube or solid state). Spending a lot of time in the studio, hearing the live feed as opposed to the recording, how different mixers, speakers and amps behave will do that to you.

This is one of the intrigues of class D for me as they often lack some of the more heinous colorations that I associate with transistors and tubes. For all that, my experience is that class D amps often have their own unique sonic fingerprint that varies from brand to brand as it does in the scale of execution. Its getting control of those variables that seems to be at the cutting edge of this art.
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