crazy feedback problem

[ninjadave7]

Hey all,
I've got a Ceriatone DC30 I'm having a little trouble with. Anytime I hit a dirt pedal, if there's any gain at all, the amp starts to feed back terribly at a high frequency, say 5k. Does it with a Timmy, OD820, RAT, and with different guitars too, Jaguar and LP both. It started recently, but nothing major has changed on my pedalboard. I have a CAE mc-401 buffer that is set to unity gain.

When I tap tubes (inc. the ef86) there are no microphonics, and from the little I know it doesn't seem like a microphonic cap or resistor would do this, but maybe so? Anyways, help!

any ideas?

[Jazz P Bass]

You are going to need a scope on this one.
Minimum.

[ninjadave7]

Actually I didn't troubleshoot far enough apparently.. I think it's microphonic pickups, apparently very common on '65 Jags... I'll work it out.

[Chuck H]

You DID say that it does it with multiple guitars. If it's a guitar problem that should be really easy to determine. When the problem happens just turn down your guitars volume control. If the problem stops then it's the guitar. I thinks it's wierd that a lot of players have touble differentiating between guitar and amp problems based on the symptomes. As much as we we play through this stuff and tweak controls "I" would think it would be obvious. But I digress.

[Gtr_tech]

If there's no grid stopper on the first tube....this kinda thing can happen. Check the input circuit....