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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.
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shadorne
7,467 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.
guidocorona
4,298 posts
 
Elbroth2, what switching amps besides the already mentioned Nuforce and Bel canto have you evaluated?
mrtennis
3,295 posts
 
why is there such an obsession with class d amps?

i am not aware of any other class of amplifiers which has garnered such interest or generated so many posts.

what am i missing ? is class d an infinite pursuit ?
guidocorona
4,298 posts
 
I haven't thought about it much MRT. . . when did you first realize you were obsessing about class D amplification? . . . Impacting your life? . . . Care talking about it?
muralman1
1,527 posts
 
Mrtennis. It is no secret why dug in audio companies detest class D. On my own system, Scintillas powered by advanced H2O monos, any listener can easily detect the pollution pressed onto the music by gaudy cables, flu flu preamps, and digitally smeared CDPs.

Some people think I am being sarcastic only have to spend awhile at my home to know I mean every word.

When retailers get four grand for speaker cable hoses, they are none too quick to warm up to the new class D amps that will expose their noisy dielectrics.

Class D amps have imposed rule changes. Wires must be clean. Analog signals must be left untampered by digital slight of hand like up or over sampling. Affordable preamps must improve.

If you ever took part in the passive vs. active preamp wars here and there, class D amps are the passive preamp champion's friend. Most active preamps do mess up the sound.

Ones that don't are expensive.
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