EL84 buzz / Memphis combo

[JackButler]

Has anyone experienced a buzzing sound when certain notes are fretted on the guitar ? Would this indicate a bad EL84? Any thoughts?

I just received the amp yesterday. Must be micro-phonic!? I suppose it could be a pre-amp tube too, time to divide and conquer.

[Cam]

Had an issue with mine using reverb I first thought was a dud tube , not sure if same issue though but a piece of cardboard under the tank in the bag sorted that out nicely .

[JackButler]

No, its definitely not reverb, this is probably a pre-amp tube?! The rattle definitely sounds like metal on glass, but only on certain frequencies. It reminds me of a rattle snake...but even, unlike some rattlers.

I'm going to swap pre-amp tubes one by one later tonight. (I don't have spare el84s) I may try to record it again, I can hear it on my iPod, but it is hard to hear it when played back on the computer.

Wikipedia seems to indicate other failures include "internal vibrations" of tube elements modulate the tube's signal in an undesirable way; sound or vibration.

See Other Failures in this Wikipedia article

[JackButler]

I tried a different cab and it was gone, not sure what the fix will be... this is happening on a relatively clean voicing too with reverb.

Before trying the cab I swapped all the preamp tubes one at a time...

Ultimately a it seems to have been a pre-amp (yet another) tube in V1.

Fingers crossed...