The Future of Audio Amplification

Also, this nonsense about caps burning up early due to the switching technology is a lame attempt to scare people in an era where fear reigns supreme. Good electrolytics last a long time. Enough of this fear mongering.

In the amps or speakers?

I think there's been a great deal of improvements in cap technology over the last 20-30 years. Low inductance, and low ESR electrolytics are a lot more common.

And of course we can all hear 400+kHz, right? Yeah, right...

Maybe the question we really should be asking Kosst and George is this:

What, exactly, are the audible effects of switching distortion in a Class D amplifier, and can you give specific examples, with speakers, that you have heard this from?

Like all amps, I don't think Class D is right for every speaker, so I am open to the idea that certain speakers will perform worse than others. So, George and Kosst, ball is in your court.
Please share with us your experiences.



Best,

E

+1, Erik

Wrong!!! look at it and think again. It’s Stereophiles, there’s your hint, they’ve NEVER EVER given a Class-D 20khz square wave, as it would look unrecognizable as a square wave.

https://www.stereophile.com/images/1212AM1fig03.jpg

You are correct and I was in error- that is a 10KHz squarewave.

So that makes the scan frequecy in this example only 200KHz(!), which means the class D in question had to have been built in the **1990s**. By the early 2000s, everyone was doing well over 300KHz. That means that the bump on the leading edge is the phase shift caused by a filter that is likely at only 40KHz.
So using this as an example of **all** class D amps is still a Hasty Generalization and like any logical fallacy, is false.

20kHz is hard for any amp to do, much less well???

http://www.firstwatt.com/pdf/prod_f5_man.pdf

Look at page 17 where the FW F5 absolutely nails a 200KHz square wave at 1 watt. A lot of amps are designed to roll off at or past 20KHz more for purposes of self preservation than technical limitations. You’re always going to have that guy who wants to try Litz wire ICs and create a high power oscillator. 

I agree- but the Pass amps IMO are some of the best solid state amps made :)

Our OTLs are quite good at 1 watt 20KHz squarewaves too. And they don't care about the Litz wire; I'd be shocked if the Pass amps do!

Regarding distortion- I agree wholeheartedly that small amounts of particular kinds of distortion are easily heard. This is why I've avoided feedback in our amps; while feedback suppresses distortion in doing so it adds some of its own, and its all IMD and higher ordered harmonics which are easily heard.
But it is also true that you can build a class D with zero feedback and there are a number of them around. At that point, the limit of the distortion becomes the precision of the encoding scheme. For example if you use Pulse Width Modulation using a triangle wave to set the switching frequency, the distortion is all about how precise the triangle wave is and the speed and offsets of the comparitor circuit used. It happens that with that sort of circuit, as the amp approaches full output, it can have a form of soft clipping as the encoding scheme starts to fall apart. So the resulting amp can have very low distortion and a lack of higher ordered harmonics over most of its range.