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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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Showing 2 responses by leisure7

leisure7
2 posts
 
to anything else I've heard.

There are a lot of switching amps that are poorly designed and that do not manage RF noise. Using a switching power supply saves weight and cost, but places a major noise source next to the amplifier circuitry. It takes a lot of design effort to reduce the effects of this noise, but the effects cannot be made as small as if the power supply is a good linear design.

Colloms commits the error of hasty generalization by blaming the approach for the consequences of inadequate design.
leisure7
2 posts
 
Agree. The Gilmore Raptors have substantial linear supplies.

This is one feature that allows them to produce very little RF noise of their own. When I added them to my system, I was able to track down and ameliorate external RF noise sources in my house. It turns out that every major appliance these days has a computer and a switching power supply inside, and most of these run continuously even if the appliance is idle.

For example, our dishwasher and clothes dryer are significant RF noise sources just sitting there. Appliances such as microwave ovens and digital video recorders are obvious, but it is amazing how much the audio system improves by just switching off the power to the dryer at the breaker panel.
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