LSA Voyager GAN Amplifier

You could have measured distortion of 3 billion db down and still the amp would only sound as good as the execution and parts (the tons of things that cannot be measured yet make a serious difference in sound). 

There is no such thing as "distortion below audibility". What we hear is WAY way more than what we can measure.

This may not be the most out there thing I have heard in 30+ years in audio, but it ranks right up there, and certainly the top of the last year. It is probably just better to admit you are not an expert on what measurements can be made and what they can tell us.  I will let Bruno know next time I see him that you want to teach him how to design amp properly. I am sure he will welcome the input.

Good articles here. Components don’t need to be active to add noise and distortion.

Resistors cause Johnson noise:

https://www.analog.com/en/analog-dialogue/raqs/raq-issue-25.html

Metal core inductors cause hysteresis distortion:

If you test an amplifier using these dummy loads:

https://www.parts-express.com/4-Ohm-100W-Non-Inductive-Dummy-Load-Resistor-019-015

The Johnson noise, as well as nasty distortion drowns out everything at -92dB THD+N. You need a bank of premium metal foil resistors. I use a bank of these:

https://www.mundorf.com/audio/en/shop/Resistors/MResist_ultra/

And can measure up to -116dB THD+N with them.

But most passive crossover use garbage like these:

Here's what you find in the top of the line Revel Salon 2's. All made by Bennic in Taiwan.

If you test an amplifier using these dummy loads:

https://www.parts-express.com/4-Ohm-100W-Non-Inductive-Dummy-Load-Resistor-019-015

The Johnson noise, as well as nasty distortion drowns out everything at -92dB THD+N. You need a bank of premium metal foil resistors. I use a bank of these:

https://www.mundorf.com/audio/en/shop/Resistors/MResist_ultra/

And can measure up to -116dB THD+N with them.

But most passive crossover use garbage like these:

The "noise" from these resistors wouldn't even begin to register let alone reduce your THD+N to -92db at any reasonable amp power. You didn't state what power level you were using, so claims of distortion impact are suspect.

No need for exotic and very expensive Mundorf resistors though. There are two parameters, one is thermal modulation, and that is a factor mainly of size, and the other one is voltage dependent resistance, and that just requires the right resistor material, it does not need to be at all exotic.

Of course the speaker driver THD is -50 to -60db.