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Purifi and Hypex have better multitone at 15kHz and I can definitely hear they play much cleaner in the that range. But for the rest you are right, most of the Texas Instruments based cheap class D amps measured excellent at 1kHz here don't have that overall feedback loop and, to my ears, only...

I like your way of thinking! Is there a possibility to play with the phases of these multi tones to get lower peak-to-average ratio and drain more current from the amp, as you say, push it harder?

Did you have chance to listen to Hypex or Purify amp? How does it compare to Cambridge? I like the measurements of CXA81 at high frequencies, but in real life the high freq content like cymbals sound much cleaner with Purifi.

I think the Multitone Test is even more representative. It not only shows the impact of distortion at different frequencies, but also IMD.

To be fair, he could take a cheaper preamp, but then there's probably no Phono, Remote etc. So overall, you are right, CXA81 isn't easy to beat, especially when you want a minimalistic look. It's also a better investment if you plan to sell it on eBay when it's time to update

There's at least 5 years between the designs you compare

No, it wasn't blind. But if you are interested, you should try the tube-based guitar amp in some music store. It definitely has something. I don't know how to describe it properly :)

I've spent 10+ years (as my hobby) designing transistor-based guitar pedals and trying to get close to the sound of tube. You can make any kind of soft clipping if you put different types of diodes into the feedback loop, play with the type of clipping diodes, serial-parallel connection etc. In...

They only care about the sound that goes as the feedback to their ears, something which happens NOW. Otherwise, you cannot control your guitar, and for them, the transients are much more important than the frequency response and distortion. And I think that's why all the guitar amplifiers are...

Sorry, I didn't make it clear. I'm talking about guitar amplifiers used live and in studios. For example, take your favorite rock band and check out their amplifier gear here: https://equipboard.com/ It seems like 99% guitarists use tube amps in 99% of records we listen to daily.

@amirm would you be interested in organising such a test comparing, for example, tube and transistor amplifiers? We need to solve the mystery why musicians prefer tube amps

This simulation is not going far enough. You need to see how the imperfections in the semiconductor monocrystal create the traps for electrons and holes. These traps indeed can be considered as DC offset but only at a short period of time. And this DC offset NOW depends on what music your PA...

The amplifier will be linear as long as you can correct it with the feedback loop. During the gate lag period you cannot effectively control what is happening with the drain. It is not seen in the Audio Precision reports as you measure performance of PA with the continuous wave. So you only see...

Again, I'm not an expert in semiconductor technology for audio devices, but not in radio frequency transistors the trapping effect/gate lag can be quite long, in a millisecond range...

But it n class B, AB and D you do not drive it in linear range. You switch it on and of randomly. And depending on the quality of semiconductor and number of traps you'll have different gate lag. I wonder it this is the reason why majority of musicians prefer tube amps. They should have a very...

I believe the transient response of the passive 2 way coax speaker will still be affected by delay in the crossover

If there is a memory effect in audio transistor, the high gain multistage PA with deep negative feedback will have more memory distortion compared to a single stage PA. Just googled for it. It seems like there already are some articles: http://peufeu.free.fr/audio/memory/memory-1-theory.html

I think it's only valid for an ideal transistor (variable resistor Vs input voltage or current). The gain and phase of the real world semiconductor transistor partly depends on the power/current delivered before and after (future) the measurement. In the radio frequency world, this phenomenon...

I wonder if we measure what we think is state of the art properly. I believe all the measurements are done with continuous wave signal. So, with the very deep (and slow) feedback in the power amplifier you can correct all nonlinearities (predistortion). Is there any way to measure transient...

I think they increase the gain on purpose to make sure you get loud enough from the headphone port of a smartphone or MP3 player. I don't see the point in buying an all-in-one integrated amp with DAC etc and then trying to connect an external preamp with the 2V out. The smartphone-friendly port...