Noisy 'wires' (seriously...)

[EFK]

I guess when you open up a chassis you start seeing warts everywhere. Another one for the soon to be infamous Gibson GA42RVT - no matter what 12ax7 I put in V2, it is microphonic if I tap it, just like tapping a mic. This got me wondering, and it seems it might not be the tube: there is a wire running from the channel 2 volume pot over to pin 7 on V2, and if you touch tap or even look at this wire, the wire itself is very microphonic, again just like tapping on a mic. Furthermore, the wire which runs from the board turret to pin 2 on V2 is the same way, and a bit of static noise to boot (if tapped). Is it normal for these wires to do this? I resoldered both but they still do it.

[MWJB]

It's normal for grid wires (pin 2 & pin 7 of 12AX7) to make some noise when disturbed. Pops, crackles & bangs are not normal.

In high gain stages (preceding reverb stages etc) some noise when tapping a 12AX7 is to be expected - buzzez, whistles, whines & pops are not normal. Turn the amp & all volume & tone controls fully up & tap the relevant 12AX7 to expose any unwanted microphonics (be aware that power tubes and 12AT7 reverb driver tubes can get very hot).

[bnwitt]

It's normal for grid wires (pin 2 & pin 7 of 12AX7) to make some noise when disturbed. Pops, crackles & bangs are not normal.

In high gain stages (preceding reverb stages etc) some noise when tapping a 12AX7 is to be expected - buzzez, whistles, whines & pops are not normal. Turn the amp & all volume & tone controls fully up & tap the relevant 12AX7 to expose any unwanted microphonics (be aware that power tubes and 12AT7 reverb driver tubes can get very hot).

As MWJB states this is quite common in amplifiers. Some do it and some don't. V2 is a common culprit. Always check solder joints at the grid pins of the sockets and any components that are in line with the grids. Sometimes (not always) using a shielded wire grounded on one end can reduce if not eliminate this phenomenon.

[guitician]

co-axial wires are

The insulation between the center conductor and shield can be microphonic as you discribe and the wire can vibrate at the right freqency and you'll hear it. Kind of like a piezo pickup, where a vibration is changed into a voltage potental.