Reducing feedback

[therizky]

so here's another problem...actually just a common problem...

is theres any way to reduce feedback?...except using noise gate or stand 10 feet away from your amp?...

we(me and my bandmates) playing hard rock that had lots of palm mute sounds on each songs...and that feedy and palm mute sounds like talking to each other...its getting worse everytime i put any part of my hand too close to my strat's pickup.

well, i dunno how to explain this...but i think you know what im talkin about...Im using overdrive pedal that i created from the combination of modded electra distortion and jack orman's muff boost which i think its a high gain...high enough to create annoying feedback......

any help would be appreciate!

thanks!

[Auke Haarsma]

your question is feedback-ing LOL   

But seriously: A way to reduce feedback is to reduce the gain used. Do you really need that much gain as you currently use?

[Mark Hammer]

Possible your pickups are too microphonic?  Might be time for a little wax in there.

[Johan]

Possible your pickups are too microphonic?  Might be time for a little wax in there.

+1   

..also, if you're using reverb or delay, that will induce feedback even at lower volumes ( a trick I use when I need a tone to go into feedback is hiting the delay..)

j

[therizky]

@Auke haarsma:yeah...well...sure i need that much gain,if i don't then there wont be such a problem...

forget it,actually...im just asking is theres any technique to reduce feedback just like what we did to hum and noise problem...

@Mark Hammer:yeah i was thinking about that too,but can you explain me what do you mean by wax?...sorry to sounds retarded...

@Johan:no...i dont use reverb or delay...if distortion pedal could give super high-pitched feedback what worse?...and also i think the problem its not only on my pedal but also on my pickup...

[Mark Hammer]

Pickup coils can work by:

a) moving a magnetizable object around in the magnetic field (e.g., the string)
b) moving the magnet inside the sensing coil
c) moving the coil around, relative to the magnetic field

If some of the windings on a pickup coil are loose, and can vibrate when in the presence of higher volumes, they behave as if they were a coil moving around inside the magnetic field and generate their own teeny tiny voltage.  Those teeny tiny voltages are referred to as "microphonics" and can generate feedback as the sound from the speakers causes them to continue vibrating even though you have muted the strings with your fingers.

The classic solution is to a) make sure the windings are reasonably snug and orderly to begin with, and b) secure the windings with something that prevents them from jiggling in place.

Wider coils, like P90s or Jazzmaster pickups, can be more susceptible to microphonics because the inner turns of the coil are always more snug than the outer ones, and those outer turns on a P90 have more inherent slack to them than those on a Strat pickup.  At the same time, many feel that coils wound in a slightly less orderly fashion (normally called "scatterwound"), where the turns are NOT lined up like little soldiers in a line, have an inherently richer tone to them by not focussing all the resonance/s in one spot, and that older pickups have their legendary tone partly because of that.

The turns are secured in place by "potting" the pickup.  This usually involved dipping the coil/bobbin in melted wax and letting the wax seep into the coil.  This would fill up all the available space, and prevent any potentially loose turns from wiggling around. Some companies, and some issues, have tried other compounds, like shellac or even epoxy.  The ideal, however, is still wax because it can be remelted with a simple bit of heat, so that windings can be removed if you feel like it, ot torn coils repaired.  One of the essential aspects of whatever one pots with is that it exhibit little shrinkage over time, or else a) it brings back the spaces and slack that result in microphonics, or b) it pexerts stress on the wire and tears the coil of its own accord as it shrinks.

Unfortunately, to pot a pickup, the bobbin has to be able to withstand the melting temperature of wax without warping or losing shape.  Standard Fender-type coilforms can handle that okay, but the small plastic bobbins that make up a HB pickup generally cannot.  The end result is that SC pickups are often more likely to be "immunized" against microphonics than HB pickups.  Although, in fairness, there are fewer windings on an individual HB bobbin, so they tend to exhibit the same general degree of snugness you'd find about halfway through a SC pickup coil.

You don't HAVE to dip the entire pickup in wax to pot it, though.  I have had reasonably good luck by simply holding a candle and heatgun over an exposed coil and letting the melted wax seep in.  It may not soak in through the entire coil, but then it is principally the outer windings that pose the risk.  As well, I find that teflon plumber's tapecomes in a size and thickness that is ideal for wrapping around pickup coils.  One of the helpful properties of the tape is that you can tug on it and provide an additional snugness as you pull the windings inward.  The teflon tape will conform to the coil nicely.  A second helpful property is that no adhesive is involved.  When I make pickups (been making my own for over 25 years now), in addition to the wax, I will use teflon tape as the outer wind around the coil, and then more traditional tapes with adhesive on top of that.  That assures not only that the coil is snug and more immunized against looseness, but that the decomposing adhesive from the outer tape will never gum up the coil.

I'm not saying that microphonics definitely ARE your problem, but you'd be surprised how many pickups out there DO have problems with loose windings producing "unintended signal".

[earthtonesaudio]

A quick test to see if your pickup is microphonic is to mute the strings and talk into the pickup.  If you can hear your voice through the amp, there's a good chance it is microphonic (i.e. too much like a microphone).

[frank_p]

http://www.guitarnuts.com/technical/electrical/index.php
http://www.stewmac.com/freeinfo/Electronics/Pickup_building/a-lindyfralin.html
http://www.projectguitar.com/tut/dip.htm
http://www.projectguitar.com/tut/potting.htm

[Mark Hammer]

A quick test to see if your pickup is microphonic is to mute the strings and talk into the pickup.  If you can hear your voice through the amp, there's a good chance it is microphonic (i.e. too much like a microphone).

Well, certainly if you can hear your voice through the pickups, that is a sure sign you have microphonic troubles.  However, if you do not hear your voice, that is not a sign that your instrument is completely immune to shrieking at higher volumes.  Some of that microphonic noise and screeching comes about as the body itself shakes from high volume and shakes the pickup as a result.  That is NOT something you'd be able to do with just your voice.....unless you're Barry White, or Meat Loaf, or Bon Scott, or......

[therizky]

well,when i talked to my pickup,none of my voice get amplified...but when i knock my pickup with my pick,its get amplified and producing quite loud knock sound

is this normal?

[brett]

Hmmm....
It's behaving like a microphone.
That leaves you with two simple options and a whole bunch of complicated ones that I won't mention.

First, you  could reduce the gain or filter the distortion in your rig.  It's amazing how much gain you can take away and still get heavy heavy tones.
Second, you can re-jig your guitar with new or re-potted pickups, or heavier strings (always a good option), or play at an angle to your amp (and preferably facing away from it).

A combination of these cures is probably a good treatment, rather than obsessing about 1 aspect of the problem.


Other readers will have lots of other ideas.

[runmikeyrun]

I would say start by replacing the pickups.

[Mark Hammer]

well,when i talked to my pickup,none of my voice get amplified...but when i knock my pickup with my pick,its get amplified and producing quite loud knock sound

is this normal?

Whooooooooooooa, camel.  I said WHOOOOOOOOOA, camel!!!!

Taping on the pickups with a pick and hearing the tap is absolutely 100% normal.  Hell, when you go into a music store and try out a guitar whose controls and switching you're unfamiliar with, that's how you know what knob controls what.  So don't go planning/budgeting to replace pickups just yet.