Magnetic parts sound worse because of...

[mrfeedback]

"There seems to be this notion that this stuff somehow gets magnetized with a certain polarity. But the residual magnetization (remnance) changes polarity with the signal and the polarity it ends up with will depend on the polarity of the signal when it stopped.

But of course as soon as you turn the signal on again, the polarity of the residual magnetization changes again."

Yes, this is correct for AC parts of a circuit.
For the parts of circuits that carry varying DC current, the magnetising current varies but does not reverse polarity.
IOW, for each half cycle a particular stage current varies from a minimum to a maximum and back again to the minimum.

All semiconductor (amplifier circuits etc.....) circuit stages are current direction concious in this manner.

"The magnetic domains that grow in response to the magnetic field and are responsible for the residual magnetization can only respond so fast. As frequency increases, they become less and less responsive which means less and less distortion."

So IOW there are delay/distortion characteristics on increasing going current changes and decreasing going current changes, and they will be different according to direction of change.

Audio signals are AC with zero DC offset which means the same area under the positive and negative curves BUT audio exhibits different slew rates and different peak amplitudes wrt signal half cycle polarity.

This adds up to a magnetic zero point different to the signal zero point, and may constitute a hysterisis point.

Eric.