When someone tells you it's a $40,000 amp, does it sound better?

I’ve seen any king of while spectrum noise in different D class amps.. never sine wave! higher freq. though! higher switching freq. amps theoretically should be easier to filter noise out, but again, switching frequency generator has the same reference clock generator issues as any DAC, such as phase noise etc., thus can be heard. 

@westcoastaudiophile If the output filter is doing its job, all you'll see at the output of a class D in terms of noise will be the sine wave residual that is at the switching frequency of the amp. That typically might be from 500KHz (near the bottom of the AM radio band) up to about 800KHz.

Honestly no-one can hear that.

What one might be able to hear is knock-on effects from other equipment if the amplifier has spurious parasitics that are messing with that other equipment- RFI can do messy things with audio.

But to be fair, lots of tube amps can do this too, through the swept resonance that can occur between the power transformer and the rectifiers installed.

We spent a lot of time chasing parasitics in our design. When it was finally ready, when we did the testing of our amp it was the bridge rectifier in the power supply that was making the noise, which we fixed. That is why I said a class D amp can have less spurious noise than a tube amp- whether in the speaker on radiated from the amp through the air or thru the AC power. 

@atmasphere "Honestly no-one can hear that.” sure, if you give me $100,000 budget for output filter alone, I can design output filter with close to  0 Ohm ESR caps and 0 Ohm ESR inductors etc.. :-) 

what about reference sampling clock purity, do we need $20k World clock device for sampling analog input signal to match class-D amp with the rest of audiophile setup?

@atmasphere "But to be fair, lots of tube amps can do this too, through”

I wish you (really) good luck matching tube amp with D-class Amp! 

what about reference sampling clock purity, do we need $20k World clock device for sampling analog input signal to match class-D amp with the rest of audiophile setup?

@westcoastaudiophile 

If you mean the 'clock' for the encoding scheme of the amplifier, the answer depends on how the amp runs. If the amp is zero feedback it will be found that the triangle wave generator has to be really stable in order to prevent noise (hiss) being generated at the output. 

But if the amp is self-oscillating, the amp is immune to minor drift in the switching frequency.

I wish you (really) good luck matching tube amp with D-class Amp! 

Thanks. We think we've succeeded in that- we've been making tube amps for nearly 50 years at this point.

My gosh this has become very scholarly with respect to transients in a class D setting.

Isn't the harsh reality of class D is that it's to clinical and precise, and harsh. With class AB you get distortion and isn't that what harmonics is all about when you listen to music. It's all about the design and the colorations that are done by the amp designer. Most class D stuff is all about fitting lots of power in a small package.

And class D it's kind of cheap stuff so good luck making class d a preferable way to go