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Re: Fixing pick-up resonance?
6/9/2012 7:01 AM
Rick Payman (10061) wrote:
Such resonance or 'feedback' problems are very common when amplifying acoustic instruments. The resonances are largely a characteristic of the instrument itself, and each individual open or fretted string has its’ own natural resonant frequencies (fundamental and harmonics).
Feedback is a complex combination of all components involved in the amplification chain and feedback ‘loop’; the instrument, strings, tuning, pickup, pickup placement, preamp, effects/equalisation (if used), amplifier, speakers, positioning of the instrument with respect to the speakers, walls etc., and characteristics of the room.
Changing any one of these components will affect susceptibility to feedback at a given volume, together with the frequency and nature of the problem signal, as the different resonances contend to find a dominant feedback mode.
Starting with the instrument, I would personally only consider permanent string damping as a last resort, but guitarists do employ palm-muting techniques to facilitate playing at very loud volumes.
One common solution is to use frequency equalisation, which could be anything from a simple mixer/amplifier tone control, to a graphic equaliser, or even dedicated pre-amp which includes anti-feedback control, commonly in the form of a tuneable notch-filter. Experimentation is the key, but the adjustment need not necessarily be complicated; a simple reduction of lower (bass) frequencies may be sufficient to do the trick.
Perhaps the simplest (but not always practical) solution is to experiment with instrument/speaker placement, such as avoid having the instrument directly in front of a loudspeaker; even your body placement comes into play here!
Hopefully given some ideas to try – Good Luck!