Ampeg SVT CL Ringing Noise

[pbass1972]

My Ampeg SVT Classic Series head has an intemittent problem where it makes a ringing noise (like an old school telephone). It seems to do it more frequently when the amp is fully warmed up and particularily when you play in the upper registers. At first I thought it was a speaker problem, but then it did it when I was playing through a different cab. Any ideas?

[nysbob]

Microphonic tube in all probability. Wait until it's warmed up and doing it and tap on your tubes with a pencil...the offender will likely make itself known.

[JimmyM]

+1 for bob.

[Thumpking]

It could be as simple as a tube retention cap vibrating against the top of the tube, or one of the springs. I actually had one come loose on the way to a gig and during sound check, I could here it. Adjusted it and good to go.

[Jerrold Tiers]

Ringing, or more typically a "chains rattling" sound in the speakers is often a microphonic POWER tube........ tap on each one with a pencil sized stick and see which it is.

if you hear it direct from the head, it's more likely a tube retainer, etc.