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You are asking for a reality test

Hi

I appreciate your frustration here, perhaps if anything is clear, it is that it is not clear.

You do say “Dan and tomservo want to pretend that solidstate components don't distort, but they do! Hence solidstate components, just like tubed components add imparted distortions that color the music.”
Actually, I have not taken that position at all.
I an familiar with both, have built a good number of tube and SS amplifiers (including one that flew on STS-7 and STS51 a shuttle flights), worked at Grommes precision (a company that made tube and ss amps) in the 80’s and have been in audio for a living most of my life designing loudspeakers and transducers.
My message if any would be that this area is full of subtlety which is inconveniently complicated especially to sell from. As a result, plausible sounding explanations are often used when a factual one is to messy.

I suggest a reality test, the same one I described for testing speaker cables, works on tube and SS amplifiers too..

First, ask the dead serious question, are you after a music producer or an accurate sound re-producer?.
“Is an ideal amplifier one which adds nothing to the signal”?

If no, there is no need for the reality test, this is for re-producers only.
If yes, continue, this test reveals the difference between the input and output.

Connect the amplifier under test to the speaker, put the speaker in another room /closet etc.
If the amplifier inverts or has a floating output, this next part is easy.
Lets estimate the amplifier gain at 20dB, construct a resistive attenuator with 20 dB of loss.
Connect the input signal to one outside leg of a 10 turn trimmer pot (say 10K). Connect the attenuated amplifier output to the outer outside leg. Connect another amplifier of your choice to the wiper of the trimmer (with appropriate shielding etc) and the amps output to another speaker.

Now, the trimmer pot has the input signal on one side and an inverted version of the output signal (attenuated to be approximately the same level as the input) on the other. The wiper is tapping into somewhere in between.

With the amp under test playing music of your choice, turn the gain up a little on the second amplifier until you hear sound in the second speaker (near you).
Adjust the trimmer to get the least sound level, this is the null, the lowest point in the bridge network you have constructed.
Now (at the Null) , any signal coming from the second amplifier and speaker is only the what stuff the amp under test adds or subtracts while amplifying the signal.
In terms of the “perfect” amplifier, there is no audible residual difference signal left to amplify, it is as they say, a “wire with gain”.

Do the same test (a resistive bridge circuit) but use some signal easier to quantify than music and measure the results and you unfortunately have one of those suspect distortion “measurements”.
Weight the harmonics according to your ears sensitivity, level and masking and the numbers correspond to what you hear more closely than straight THD.

Do this test with a cheap SS amp and you’ll hear a smaller but very different sounding residue.
Find the amp with a smallest amount of residual difference and you have also found the one contributing the least to the sound.
Make sense?

Tom





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