is it the tube or the circuit? the 12ax7 as a preamp tube is driven at ridiculous high gain levels and max heater voltages in an effort to squeeze more out of it, which shortens life (especially in instrument pre-amps) the 12ay7 is lower in gain to begin with.
i say look at how it's being used before you jump to a conclusion the tube type has a "tendancy" to microphonics.
i say look at how it's being used before you jump to a conclusion the tube type has a "tendancy" to microphonics.
My experience is that it is often the very high gm pentodes which are microphonic. Try 6s17k for zero microphonics.
6S17K is zero microphonic, but it can't substitute 12AX7 because it's grid is too close to cathode, it's grid current is much higher. I use them with grounded cathode, and bias by 47k and it's own grid current. Excellent for new design in phono and microphone preamps, but can't replace 12AX7.
Most of the Russian "EV" types are pretty nice tubes that aren't very microphonic. The best 12AX7 you can get is actually the 6N2P
I agree !!!
The 6n2p-eb is very quiet. I use them in my phono-pre.
Others I tried, in especial new chinesse (MkII) with frame-grid tech, are like a bells.Horribles!!!
Cheers
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