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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
dazzdax
599 posts
 
Elberoth, I like the ICEpower amps better than the Mark Levinson 333 or the Accuphase A-50V. Not because I like "sterile" sounding ICEpower. To me the ICEpower amps sound more transparent, dynamic, faster and less colored compared to the artificial ("mechanical") sounding ML or the slow and a bit opaque sounding Accuphase. This is certainly not hyperbole, this is my own experience, which is somewhat comparable to the experience of the fellow audiophile who preferred ICEpower than his ML 33H's! Or is it likely that we are suffering hearing impairment?

Chris
audiofeil
4,011 posts
 
Agreed. Class D technology is in the infancy stage.

There are some combinations of D amps and speakers that work well but they are exceptions to the rule.

There is no SOTA Class D amp vis a vis the best SS/Tube designs.

None.
muralman1
1,527 posts
 
Audiofeil and Elberoth2, The class D amps I have surpassed solid state amps costing 3 times as much by a wide margin in my system.

Not only that, these class D amps have uncovered a nest of attending components as the snakes they are.

That is because they have so little personality of their own, and as Dazzdax pointed out they are wicked fast. Minute details get through, both signal, and distortion.

You just don't know the beauty of class D if you match them with tried and true conventional gear.

audiofeil
4,011 posts
 
Vince,
Perhaps you missed this in my post:

>>There are some combinations of D amps and speakers that work well but they are exceptions to the rule.<<

Thanks.
shadorne's avatar
Ag insider logo xs@2x
shadorne
7,477 posts
 
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.

Theoretically, since Class-D depends on utlra high speed circuitry it looks like it might be superior in accurately tracking a complex waveform - an extremely linear device that is very cheap and stable.

My concern would be EM/RF noise from the rapid firing of high power MOSFETs in this configuration and how to keep this noise away from power supply rails and everything else. Fundamentally the firing on the MOSFETs is modulated by the audio signal, which suggests thst any noise might highly correlate with the audio signal rather than being random thermal noise...

For a subwoofer this will be less of a problem than for a full range speaker, of course.

I expect Class D will become the norm in future due to progress and the high efficiency.
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