My NAD 3020 D proves your Class D tropes are wrong

Technics is the curious case of feed-forward design. :) Kind of sort of.

It depends on which part of their website you're paying attention to :)

Are you working on any Class D amps?

Yes. Its one of our own design- we're not using anyone's modules.

Class D feedback works so differently than linear amps that I have trouble believing the amount of feedback behaves the same way, but what do I know?

As far as I know, feedback is fundamental to Class D. It simply can't operate without it.

@erik_squires You are working with a misconception! You can (and some do) operate class D amps without any feedback at all. Up until a year or so ago, that was how all our prototypes worked. Feedback isn't used to construct the output of a class D amp, and you can have output with no feedback. IIRC the Merill class D is a zero feedback design; Technics claims that their amp is zero feedback too.

I do not believe you can hear any difference in normal home listening from equivelant models with A/B power.  

The class of operation isn't important. How much feedback the amp uses *is*. This can have an enormous effect on how much and what kind of distortion is present. Distortion is a good deal of the reason we hear differences between amplifiers- that old trope about 'distortion is negligible and therefore inaudible' so often seen in reviews of the last 50 years is false.

I find myself less willing to type with the same precision and care that I used to.

I get accused of being overly specific more than I used to...

Going along with that, there is something about some Class D that requires DAYS to warm up.

@erik_squires I missed this earlier. This is not true of all class D amps. I'm not contesting that this is your experience with your amp, but its nothing to do with class D- its something to do with your amp.

I can always hear class d amplification because it is so tonally off that it is like fingers scratching on a chalkboard to me.

I just listened to a class D yesterday that was more focused and just as relaxed as a good tube amplifier. So I very much doubt this statement- it is trolling IMO.

Class D is used in most powered subs which is not to say it can produce high frequency well.

This probably depends on what is meant by 'very well'. I listened to two amps yesterday, one tube and one class D. They both have less than 1 degree of phase shift at 20KHz. The class D amp has over an order of magnitude less distortion than the tube amp at that frequency. But its primary distortion product is the 2nd harmonic, and enough that just like a tube amp the 2nd is able to mask the presence of the higher orders. So it sounds like a tube amp, although considerably more neutral owing to lower distortion overall and the ability to act like a nearly perfect voltage source.

But not all class D amps are like this. They have as much variance from model to model and brand to brand as you see in tube amps, which cover the gamut of SET, OTL, push pull triode, push pull pentode and so on.


The bottom line is you have to be careful about making blanket statements; in the world of class D as in almost any other topic blanket statement are so general as to be rendered false.