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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
simontju
257 posts
 
Hello,
I would respectfully disagree with Atmasphere words, if not all then vast majority. Class D designers and manufacturers are not for iPod and such alhgough I will admit that Spectron, for example, is designing, now, amplifier with 50 watts rms power with size less then postal stamp - as one of the project in professional audio. On other end of the spectrum Spectron is developing (compact!) 8000 rms amp for Inter-M, where Spectron won the contact against Bang and Olufsen (ICE), Philips (Hupex) and others.

No, class D was not design to work against heat. Spectron chief designer John Ulrick designed it in 1974 (so its not so young technology either!) to drive bass modules in his (and Nudell's) Infinity speakers - which I believe were accepted rather well ay that time.

I am AND engineer (digital signal processing) AND professional musician (graduated conservatory class piano centruries ago) and I can't imagine any audio designer who build amplifiers that cannot handle speakers with huge phase shifts and yet cause the chill down my spine when I hear the real piano sound in my listening room ( not heavenly piano glorified by 2nd and other even harmonic distortions nor one made out of steel or other metal with all non -existing details).

All The Best in Your search of perfection
dazzdax
599 posts
 
Vince, haven't you ever heard of Ralph's amplifier brand (Atmasphere)? :)

Ralph: my ICEpower based amps (ASP1000) have a bit aggressive and forward sounding treble. Do you know a cure for this? Will it sound better when I would use some kind of autoformer like the one from Paul Speltz (Anticable, Zero autoformer). Sorry, I'm not a techie so I can be totally wrong...
Btw, my current speakers are Dunlavy SC-V's.

Chris
audioperv
18 posts
 
"There is a common myth in audio that there is no 'best'. However, the English language tells us that it does exist- else the word 'best' would be meaningless."

Interesting Atma, I did not know you were a nominalist. . . . I thought that particular philosophy had been abandoned a few hundred years ago. By the way, I do not own a switching amp. My amps are 20 years old solid state class A/B JRDG model 7M monos.
muralman1
1,527 posts
 
Simontju, No, sorry, I am not familiar with most name brands of tube amps, since I am not shopping there.
muralman1
1,527 posts
 
Atmasphere, class D has, in fact, secured the boombox audio field for the very attributes you listed. That says nothing of the class D amps that have been designed for the 2 channel audio connoisseurs, anymore that the previous mass product use of tubes defines your products.

The most fussy tube amp I have heard is the Audio Note Kageki. As I understand AN takes pains to limit compromises for their upper shelf amps.

ICE makes the 500A amp module. This is a module that requires an add on power supply, unlike the ASP modules that have digital power supplies built in.

The 500A module is aimed at the tiny audiophile market. You'd think that would be it. No, they spent countless engineer hours improving the 500A module. You may consider this production in agreement with your reduced compromise ideal. Why did they do that? They wanted to limit compromises in their finest module.

Now, the 500A module's amp performance depends on that amp designer's talent and knowledge. And better sound doesn't stop there. That designer amp's performance depends entirely on it's owner's application. I have found the requirements of a successful class D system are stringent indeed.

The better of class D amps CAN be frightfully outer space transparent. The down side is any, whether it be electronic, like oversampling DACS, or physical, like hose speaker cables, the result can be disastrous. That has been my experience.

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