Class D amps that are superior to all or most?

but many hear some thing not quite right with Class-D in the upper mids/highs with many speakers, and this is it’s Achilles heel.
Technics (SE-R1/SU-R1000) claim to get rid of it by making the switching frequency 3 x higher, 1.5mhz, so that then the output filter is also 3 x higher and therefore it has little or no influence down into the upper mids/highs.
Most Class-D’s that have around 600khz switching frequencies, have output filters that have effects down into the upper mids and highs.
And yes throwing a **** load of feedback may fix it, but the best amp "theoretically" would be ones that use no feedback if it can be done without distortions, or very little or local not global.

Complete rubbish.

I've explained this many times on multiple threads. Its apparent that faced with facts, George is at a loss; his comments are far too inclusive.


The output filter will have an effect on phase shift in the audio band **if the feedback is insufficient**. So if you see a class D amp that has lots of phase shift in the audio band now you know why.


To prevent phase shift you can do it two ways: have loads of bandwidth (that's how we do it in our OTLs, by going well past 100KHz at full power) **OR** by using enough feedback that phase shift is corrected (which is in excess of 35dB). 


Some class D amps that switch at 500-600KHz sound great and others do not. Its very much like the difference between a type 45 SET and and 750 watt behemoth push-pull tube amp- they are two different things and sound different as a result. Class D in general is no different in this regard.


The last paragraph is really terrible. You don't 'throw a load of feedback' in an amp to fix the amp, you throw a load of feedback in the amp to *fix the feedback itself*. There is a profound difference; to start with you can't just keep adding feedback as you need gain in the amp to do that and each stage of gain degrades the phase margin of the circuit. So it requires a bit of finesse.


To get the required amount in a class D, you have to resort to self-oscillating circuitry (which is also helpful for keeping noise down as opposed to a zero feedback class D design). As a challenge to George: why not work out the oscillation criteria and get back to us here? If you can't don't feel bad, just allow the lesson to sink in that there is far more to this than you think!

https://ibb.co/gt4qW9x

Challenge your self, nothing I said was aimed at you, yet you took it to heart, wonder why.

Whatever, your new class-D will tell if it’s remotely equal to the better high A- biased linear Class-|A/B amps, if it ever sees the light of day.

Since the BASH patent ran out last year, things will slowly evolve and change. For high end audio, or for ’quality’ oriented applications, class D is likely to go the way of the dodo bird.

As in: extinct.

BASH will be re-worked for high end audio and will be found to be superior to all possible class D amplifier designs. No output filter required, for one. And some other great potentials.

It always was sonically superior, in potential (on paper), to anything built and designed akin to a class D amplifier...but had been relegated to cheap Chinese design and build due to predominant use in sub woofers and similar high powered low frequency applications.

Then the associated IP ownership and lockout of the basic BASH patent. Which was Asian held. (purchased from the Canadian company that created the BASH design).

The design is open technology now re patent violation prosecution.

It was likely not done before as the patent would be waved in front of the given designer (via  western patent office representation, where it is also held)  and they would have to pay for the use of the patent, if it was available to do so from the holders of the patent.

Secondly, the lack of respect of IP in some corners of the asian build and sales world re amplifier circuitry. As in, make a superior bash based design, publish it, get sued and cut off from it all... all while asian companies steal the design and issue it themselves. Not an attractive scenario to get involved in. Thus, wait for the patent to expire, to avoid at least the being sued part. Expect the theft, and maybe find a way to ride the thing a bit, re being paid for the expected technological theft.

Expect the BASH inquisition to arrive on the Class D shores...eventually.

Challenge your self, nothing I said was aimed at you, yet you took it to heart, wonder why.

I'm not angry George, just disappointed :)   I often heard problems with class D some years back- weak bass and the like as you've described. But it was obvious to me even 10-15 years ago that class D was a tech that was on a research and development sigmoid curve- and a rising star on which we should keep our eyes. I commented on that often on this site in the past. Its now evolved to the point that a good class D amp is a player against any other amplifier technology, and has already eclipsed them.


I certainly don't/can't take it personally since at the very least none of your comments apply to any of Bruno Putzeys' designs (UCD, Hypex or Purifi) nor ours (and probably a few others for that matter).

Good for you Ralph, you need a different income stream direction now, with tubes waning.