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I've found an article about memory distortion issues in audio analog amplifiers. Available for free here.

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The author uses in the last configuration a CFP differential input with a cascode of FET controlled by the input and the feedback.

I want to use the same method on the Voltage Amplifier Stage (VAS), to provide constant power:

enter image description here

I used a CFP Vas with a cascoded MOSFET. Is this possibile? Is this good? Is the principle of memory distortion correct? Does what I'm doing make sense?

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  • \$\begingroup\$ so, when asking "is this good", it might make sense to explicitly state your goal. You seem to want to build something with memory distortion, is that correct? \$\endgroup\$ – Marcus Müller Jan 2 '20 at 12:11
  • \$\begingroup\$ Is the principle of memory distortion correct? Do aliens exist? Was there ever life on Mars? Do people make up things to sell stuff? What motivates people? \$\endgroup\$ – Andy aka Jan 2 '20 at 12:26
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    \$\begingroup\$ @Andyaka you're not funny. Not much material is found about this type of distortion, I asked if it was relevant. \$\endgroup\$ – Sam Junggiddi Jan 2 '20 at 12:31
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    \$\begingroup\$ @SamJunggiddi I have to contradict, Andy can be very funny; anyways, that's not the matter here: You can't ask whether a physical concept like memory distortion is "correct"; that makes no sense. You can ask whether your approach to reducing it is correct. \$\endgroup\$ – Marcus Müller Jan 2 '20 at 12:38
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    \$\begingroup\$ @MarcusMüller Sam does not ask whether the distortion is correct, but whether the principle is correct. It could be the case that there is distortion, but it's for a completely different reason. It is also surprising to me that there are so few references to "memory distortion" - maybe it goes by another name, maybe the audiophiles made it up, or maybe only the audiophiles care enough to analyze and fix it. \$\endgroup\$ – user253751 Jan 2 '20 at 16:51
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That's an old site I had maybe 20 years ago. I had forgotten about it...

In retrospect I guess this memory distortion thing was just a red herring. This kind of stuff pop up periodically in the audio community, someone finds a magical reason that explains everything, it gets popular then is forgotten then it starts all over again with something else.

Sure, if you want an opamp with quick settling time to high precision and low thermal tails then you need an input stage that doesn't get any temperature imbalance, especially when it handles strong input signal. But is that important for audio? Probably not!

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    \$\begingroup\$ Straight from the horses mouth. \$\endgroup\$ – Andy aka Jan 2 '20 at 14:33

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