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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
mrtennis
3,295 posts
 
hi guidocorona:

i have attended ces shows since 1992. i have yet to hear a class d or solid state amp that i would want to own.

i have not heard any class d amp i would characterize as dark. of course the sources that i used to evaluate stereo systems were probably different from what you auditioned.

i am still curious as to which brand(s) you found "dark" sounding. in addition, i am also interested in the names of other components and stereo systems which you consider to be "dark" sounding.
guidocorona
4,298 posts
 
Hi Vince, excellent point about dwindling NOS tubes. . . eventually these animals should be declared endangered species and given a modicum of protection against careless use by heartless audiophiles!

You have good chances of being correct about the future of class D amplification. Yet, it is a lot safer to study evolution with hindsight than using foresight. . . . at least for old and crotchety 'secular humanists' like yours truly. Perhaps 65 millions years from now some bookish techno-paleonthologist will examine the then famous Silicon-boundary layer in ancient petrified garbage dumps an discover an explosive growth in the fossil record of switching amplifiers. And perhaps a fossilized 'organism' with an especially unusual body plan sporting a transformerless combination of pre-silicon B-300 tubes and primitive switching amplification modules will be uncovered. . . a brand new techno-phylum will be assigned to it. . . and the specimen will be named Hallucigenia Atmaspherii by its discoverer--an incredibly distant descendent of Aloysius Qwantz Schmaltzenstein Gavronsky.
rf_gumby
54 posts
 
It's kind of silly to have to drag out the "dwindling supply of NOS tubes" argument. There are more tube manufacturers than 10 years ago thanks to the music and hifi industries, and MANY manufacturers (basically all) use current production tubes and get excellent sound from them.

Yes, you can likely improve the sound with some pricey NOS tubes, but the costs are going way up and you tend to simply change the sound with differing tube brands and vintage, not always for the better. I have a pretty good stash of NOS tubes, but I could live just as happily if my rig was running current production stuff.

RFG
muralman1
1,527 posts
 
Guidocorona, fellow secular humanist, you are right about the futility of guessing evolutionary trends. I am sure you picked up on that fool's recent surmising there will be two races in 250 years, tall and swarthy haves, and ding dong dwarf have nots. Who can say? Given the world's species environmental peril, I have darker predictions.

Just the same, I think if I were a struggling proto-mammal 240 million years ago, after spying a sleek early dinosaur..... I would put my money on him to rule the world for the next 200 million years. Don't you think? :D
atmasphere's avatar
atmasphere
11,785 posts
 
We have an internal design rule we call the 20-year rule that prevents us from using NOS tube types, IOW the tube type has to be in current manufacture. We've had this from the beginning, so its already served us well, as we have an aggressive update program for our older products.

Its a simple fact that semiconductors go obsolete and out of production at light speed relative to tubes. You can still buy new manufactured tubes that were designed 60 years ago, but I can think of quite a few semiconductors designed in the last 10 years that are already long gone.

The 'dwindling tube stock' idea is a red herring, unless a manufacturer has chosen to design around a tube that is no longer made, a foolhardy undertaking.

As a lot of the current class D amps are on monolithic modules using proprietary semiconductors, you can expect that if you need to service the amplifier in 10 years or the like that the device is going to be tricky to find. This is one sure way of knowing that the technology is still on its way up.

To get a better understanding of this, an example of a mature semiconductor technology is the lowly op-amp. You can still buy TLO82s brand new, despite their having been designed in the 1970s.

How many people on this thread think that they will have the same class D amplifier ten years from now- knowing full well that in far less time than that their amp will be superseded?
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