Amplifying Your Guitar

Why does my guitar feedback when amplified?

NB: You should not experience feedback at low or normal amplified volume levels.

For years, luthiers have been trying to make acoustic instruments as resonant as possible. Using solid timbers - as Faith Guitars do - is one of the very best ways to do this, and as the instruments are 'played in' and as the wood matures, one would expect it to be become more resonant and sweet sounding. This is basically because the wood is gradually moving more freely, and is exactly what you want from an acoustic guitar!

Likewise for many years, musicians have wanted to amplify their acoustic instrument. But they have often encountered the dreaded issue of on stage feedback when they get to a certain volume. This is essentially why solid body electric guitars became the obvious choice for rock n roll bands..

Plus, every guitar has its own 'resonant frequency'. So sometimes you will find that a certain note sets off the feedback more than any other. This is simply because your guitar is sympathetic to that frequency, and in itself, nothing can be done to change this. But over time, you may find that the resonant frequency changes, as once again the solid timbers mature further.

The bottom line is, the more resonant the instrument is, the more feedback you may experience at higher volumes. It is a sign of a good acoustic instrument.

So, how can i combat feedback?

  • Use a feedback buster or feedback blocker. These cover up the soundhole so that less sound can get back into the body of the guitar to be picked up and amplified again, thus creating a feedback loop.
  • If your instrument has a 'Phase' button on the preamp, this usually does the trick. If you experience feedback, then a push of the phase button will enlist the help of some simple physics which will cancel out the frequencies that are causing it.
  • Use a microphone instead. Most professionals will always record their acoustic guitar with a mic in a studio, and doing the same on stage will allow the sound engineer to control the levels and therefore eliminate the problem. Plus, you will get the real acoustic sound of your guitar - which is why you bought it in the first place.
  • Don't drive the preamp on the guitar too hard. We would recommend that the volume knob should be no higher than 3/4 (3 quarters). It is better to drive the PA, amp etc than the guitar itself.
  • Don't stand too close to the amp. Obvious, we know.
  • Make sure the pickup under the saddle is making proper contact with the bottom of the saddle and the bridge. The pickup should lie flat with even contact all along its length. A guitar tech could check this out for you. If there are gaps between the bridge, the pickup and the saddle, then this can cause its own little feedback chamber.

However, after a few particular guitars stubbornly refusing to comply with feedback busting techniques, we experimented and found the following:

  • The Shadow Nanoflex pickup cables are intentionally microphonic and should be clipped into a plastic clip about an inch or so after they come through the bridge into the body. This clip stops the microphonic properties from that point forward. So you get a basic microphone effect as well as the undersaddle pickup tone.
    So... If the cable is not clipped properly (if it slipped out etc) then the cable would act as a big microphone in the body and is likely to feedback a lot.

If the pickup cable is clipped appropriately – which it probably is – then the one more thing to try is:

  • Nanoflex Pickup Cable oscillation: (The Putty)
    The pickup cable comes through the little hole in the bridge into the body cavity, sometimes the resonant frequency of the guitar causes the pickup cable to oscillate in the hole causing what seems like feedback. With the simple addition of a little putty inserted into the hole (from the inside of the body), it stops the cable from being able to oscillate, and improves the situation.

    The above solution has been fitted as standard to all Faith Guitars with Shadow Electronics for a number of years now. So if you see putty or tack on the underside of the guitar bridge, don't worry. It is supposed to be there.
    As some instruments are naturally very resonant at certain frequencies, it can’t be engineered out.
    The Putty is made by the 3M corporation and will be either white or blue, and is supplied by Shadow Electronics with all Nanoflex equipped preamp systems.