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How do I reduce guitar feedback?
March 23, 2010 8:21 PM   Subscribe

How do I get rid of this horrible, high-pitched feedback?

I recently acquired a cheap Tele knockoff which I proceeded to fix up. I put the pickups and electronics from a Baja Telecaster (S-1 switching system, Twisted Tele Neck pup and Broadcaster bridge pup) in place of the crap that was there before. After I had finished setting things up to my liking I had a pretty sweet sounding guitar with a full, really alive tone, but as soon as I tried using it at full volume with my band, problems arose.

When I apply gain it makes a horrible high-pitched squeal, even when I mute the strings. I've been doing some reading around, and it seems to be what is referred to as microphonic feedback. This happens with my other guitars as well, but I've always been careful to manage my volume and gain settings so that it doesn't. This guitar, however, seems to be much more susceptible. It doesn't seem to matter much what pickup I'm using, the squeal always returns as soon as I apply gain-based effects.

If microphonic pickups are the issue here, shouldn't I be able to hear my voice if I talk into the pickups? When I tap the body or the pickups with a pick, I can hear it, however.

This is a single-coil guitar, of course, but so are my other guitars, mostly. The pickups are relatively recent and come from the Fender Custom Shop so I don't think they're shoddily constructed. I've heard that potting/re-potting the pickups can help, but I'm not sure that's the issue here. I soldered the whole thing myself, and I'm pretty inexperienced at that sort of thing, so maybe I screwed something up in that area, though I did follow the wiring diagram. I don't think it's a grounding issue because it makes no difference if I'm touching the strings. Could it be bad shielding then?

I've tried moving further away from my amp, but it doesn't really work - at least not in our practice space. I've tried reducing volume and gain, but the feedback only disappears when I'm down to unreasonable volumes (to my ears, anyway). We do play pretty loud, but I've been doing this for a fairly long time and thought I had pretty good control over feedback.

I guess these are my questions:

Should I re-pot the pickups?
Is this a wiring issue - improper shielding/grounding?
Should I buy a noise gate/equalizer/feedback destroyer?
Should I just buy a ukulele?
posted by Zero Gravitas to Media & Arts (6 answers total)
 
Pull each of your pedals/effects out of the signal chain serially and try it each time. Suggest you take notes.
posted by Ironmouth at 8:33 PM on March 23, 2010


Repotting the pickups would lessen the microphonic effect. Basically, they're floating freely & the vibration from the amplifier is resonating with the pickup in a sympathetic way.

Buying some sort of phase inverter (common for acoustic guitars where this type of feedback is very common) may also help. The phase inverter will reverse the signal coming out of the guitar, so the vibrations coming out of the amp won't be sympathetic to the guitar. I'd find a cheap phase inverter first (perhaps you can build it in to the guitar) and if that doesn't work, try repotting the pickups.
posted by MesoFilter at 8:36 PM on March 23, 2010 [1 favorite]


The phase inverter sounds pretty interesting. Can you recommend any one in particular that I could order online? Also, I'd be interested in putting it in a pedal, so that I could use it with all my guitars.
posted by Zero Gravitas at 2:38 AM on March 24, 2010


Hmm, no recommendations, but I'm sure someone's put this in a pedal. If you want to get serious, you can try the IBP Phase rackmount (but they're serious money).
posted by MesoFilter at 12:32 PM on March 24, 2010


Point the speakers away from the guitar. It isn't the amplifier per se, it's the sound from the speakers that reaches the pickup and causes the feedback.
posted by exphysicist345 at 6:08 PM on March 24, 2010


Since it happens with all your guitars, I'd hazard a guess that you have a tube amp and the tubes are going microphonic. Which is nasty.

Microphonic feedback isn't (shouldn't be) caused by single coil pickups, and especially wouldn't be consistent across multiple guitars.

Inverting phase on a 5kHz squeal is a difference of 3.5cm, so it likely won't help a microphonic problem if it were occurring in the pickup. (It would tame "musical" feedback at ~500Hz, though.) Also, if the feedback *is* at the amp, phase will do nothing.

Free test: Get a long cable or wireless rig. Drive your amp into microphonic feedback. Step out of the room, or get as far away as you can. If nothing changes (pitch or amplitude), it's definitely in your amp. Get everyone out of the room first, as no one wants to be listening to this test.
posted by lothar at 9:01 AM on March 30, 2010


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