What other than too much gain can cause amp/guitar to feedback too much?

[hunter]

I am really happy with the tone of my XTC, but there is one thing that bugs me. If I turn it up with the metal band, I need to be very quick with the volume pot on the guitar or I get uncontrollable feedback (in blue and red channel with the boost on).

I don't think I have too much gain on, but still this is happening.

Could it be related to a microphonic preamp tube or something? Any other ideas?

[_tom_]

Microphonic pickups or preamp tube maybe?

[Twinfan]

Microphonic pickups would be my guess......

[MDV]

It is a horrible high pitch screech or lower?

Horible high pitch screech is probably microphonic pickups.

Lower is probably just strong magnetic fields compressing and distorting each other being noisy; it happens with even quite modest levels of high gain. Proximity and orientation of guitar to amp and other electrical gear around affects it a lot.

[hunter]

It's not the ultra high kind of ear drum killer, but rather the lower highs/upper mids one.

Hmm, is it possible that Cold Sweats are microphonic?

I was just experimenting around and I think swapping preamp tubes improved it slightly. It's hard to test at home as it's SO LOUD.

But I thought that it improved much more when I pulled the fuse for two of the four poweramp tubes. I put the fuse back in and thought when tipping them that one of the four tubes was making more noise than the others.

Is it possible that a poweramp tube causes this kind of feedback?

[Twinfan]

You'll need it fairly loud to get the pickups feeding back if they're microphonic.  Best way to check is get it set up with the PRS so it happens, and then swap guitars.....

[hunter]

You'll need it fairly loud to get the pickups feeding back if they're microphonic.  Best way to check is get it set up with the PRS so it happens, and then swap guitars.....

It seems more with the SG than with the PRS, but then CSs have more treble and output than the RYs, I mean I would turn up presence and gain probably when swapping the 2 guitars. I really have the feeling it was one of the power tubes, but not sure.

[HTH AMPS]

Its just something you get with high gain amps... lots of gain + volume + proximity to the amp = feedback.

Get an ISP Decimator and be done with it - they're fantastic pedals.

[dave_mc]

decimator's great- i would say, though, that if the pickups truly are very microphonic, the decimator isn't going to cure that.

[HTH AMPS]

decimator's great- i would say, though, that if the pickups truly are very microphonic, the decimator isn't going to cure that.

agreed, though I'd be surprised if the Cold Sweats have gone microphonic.

you could look at selected (for low noise/microphonics) ECC83s for the amp - Watford Valves, among others, do this.

[Twinfan]

That's assuming a preamp valve is the problem............

[HTH AMPS]

I just meant in general for lower noise

[hunter]

Hmm, today I played with the top 40 band, smaller room, lower volume, noise and feedback were really good/low, though I played the McCarty. Maybe I'll try the PRS with the metal act next time, and run the amp on 50W, let's see what that does.

Selected preamp valves in V1-V3 might also be an idea, let's wait a bit.

So power amp valve cannot be the reason?

[Nadz1lla]

I found once that this happened and turned out something as simple as the electrics were just poorly earthed. Might be worth checking the simple things like that before thinking about the more expensive options.

[dave_mc]

decimator's great- i would say, though, that if the pickups truly are very microphonic, the decimator isn't going to cure that.

agreed, though I'd be surprised if the Cold Sweats have gone microphonic.

oh yeah, of course. :)