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Vacuum capacitors

Posted by sser2 on March 15, 2017 at 17:13:53:
I have no doubt that vacuum capacitors are closest to ideal. One of the reason why tubes sound better than transistors is that their interelectrode capacitances are of highest quality, whereas those in semiconductors are of the worst.

What I meant weren't purposeful vacuum capacitors, like those that HAMs use, which are indeed too bulky to be useful in this role. The simplest neutralizing capacitor would be a dud tube of the same type, however, with tubes like 2A3 this is also clumsy. But there are smaller tubes with relatively high inter-electrode capacitances that won't take too much space, like 7-pin 6 volt full wave rectifiers or sub-miniature pentodes.

Microphony problem in tubes used as vacuum capacitors is the same as it is in tubes used as amplifiers. A 6X4 or a sub-miniature pentode would be virtually free of microphony if used for neutralization in a 2A3 power stage.