I saw an ad on the back of Elector magazine for a PWM audio amp.
I thought those things still didn't have much of a high end? Or has the state of the art advanced while I was playing with other bits of high tech?
The ad did mention "sound comparable to vacuum tube units", which I took to mean either "considerable distortion" or "sounds like crap, but there'll be some fanatic in the room claiming it sounds good".
Nothing fundamentally new was discovered in that area since the 80x, however the power FETs were dramatically improved.
The THD of 0.05% is typical for modern Class D with feedback. It is quite possible to achieve the distortion better then 0.005% and still have the good efficiency with the careful design. Of course, the linear amps can do better, however our blind listenning tests show that no one can hear any difference below the distortion level of 0.1% or so.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
It sure seems that switching speeds have gone up dramatically in recent years.
So does it work for "audiophile" quality, "decent stereo" quality, "kitchen radio" quality, what?
And I haven't messed with class D for so long I am happy with "1960s transistor radio" quality. Anybody got a link to a basic treatise on really simple class D design?
Jim
-- "It is the mark of an educated mind to be able to entertain a thought without accepting it." --Aristotle
Nothing gets to audiophool quality :-) Just say decent stereo. I did a class-D design about 10 years ago (using a HIP4080 IIRC) and back then it already sounded just like a normal amplifier.
In most sound systems the speakers add more distortion than the amplifier. Phase response is also an important factor.
There is no doubt that you can have decent audio quality with the properly designed class D. The "audiophile grade" is the question of beliefs, not technologies. The "boom box quality" is accomplished with the digital Class D without feedback.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
Yes, here you go:
Here is another one:
...however those amps only look simple. I can guarantee that it will take some effort and experience to make them work as good as advertized.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
Pioneer's "Elite" series uses a Class-D driven design.
Distortion figures on lower end products from most consumer level makers these days doesn't even get declared. In most cases, it is 0.1% or higher.
One can buy 35 Watt dual channel "chips" that are D class. They make great front ends for HV power supplies. Pump that transformer with pure sine waves... warm, fuzzy feeling...
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