#1
I got a used Rockerverb 50 combo from a guy on Reverb. It sounds killer, but some times when I have the dirty channel cranked, it makes this odd pinging/ringing noise that is just barely audible over the amp's intended sound. It seems to be coming from inside/behind the amp, and it only happens when I'm actually playing a note/chord. If the guitar is muted (and often if its just quiet) this noise doesn't occur.
I don't really mind it just practicing by myself, but it would get annoying at a live show and makes recording with it a no-go right now.

I messaged the guy who sold it to me and he said that the most likely problem was the tubes coming loose in the shipping process. This is my first tube amp and I'm not really sure how to check this, or how to tighten the tubes if this indeed the problem.
Researching this issue, it seems like most others assume the problem is dead/dying tubes.

What do y'all think?
Custom-Built Strat
Epiphone Les Paul Custom Pro
Orange Rockerverb 50 Combo
#2
It sounds like you have one or more tubes that have went microphonic. I'd start with buying a few new 12ax7's and rolling them through the preamp so you can see if that fixes the issue.

But you push the tubes directly in and pull them directly out. sometimes they can be stubborn and you have to gently rock them side to side while pulling them out. remove the chassis from the head shell first though

Nice step up from the MG
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
Last edited by Robbgnarly at Feb 11, 2016,
#3
It may also be that you're slightly out of tune and generating a harmonic.
“Ignorance more frequently begets confidence than does knowledge.”
Charles Darwin