Killing Microphonic Feedback

[kevinT]

most feedback is coming from the cover, not the coils, unless your coils are real loose. covers we get aren't flat so there's space between the cover and the slugs, and thats where the squeal comes from. I sometimes clamp the cover on real tight then solder, but unfortunately this spreads the bottom of the cover out, but it does help with microphonics more than just putting the cover on and soldering. Old PAF covers were flatter than what we get now but not totally flat at least the one I have. Tom Holmes covers are dead flat, all sides are dead flat, they're the best I've seen so far....

Are you using anything for padding to dampen the vibration? ...silicon caulk?

[Mystic]

I also use a little stick glue under the magnet.

[SK66]

I think we need to clarify terminology. This is not microphonics, this is harmonic feedback. Sometimes due to pickup components/mounting, sometimes due to stings/guitar. Even an unmounted pickup will give harmonic feedback when placed very close to an amp. The speaker magnet is very strong and the amp puts out an EMF signal. The pickup senses this and then outputs a signal which the amp then amplifies and so it starts.

Microphonics is when the coil windings themselves move when exposed to vibration (sound waves). The coil winding moving creates an output signal functioning like microphone. I've never seen microphonics in a pickup which was adequately taped or potted, other than very old pickups where the potting has broken down and resulted in loose windings.

[Dave Kerr]

I've been using snot tape for all the prototyping I've been doing lately, it's very high tack and conforms nicely to irregular surfaces, helps fill in the gaps for all the sloppy one-off bobbin cutting I've been doing.

[Possum]

...

what is snot tape?

[Dave Kerr]

snot tape

3M Scotch or Permacel 1/2" ATG Tape is also known within the film biz as SNOT TAPE and is used to affix lighting gels to their frames and camera assistants use it sparingly to affix wratten gels to the rear of lenses. The ATG Dispenser, sold separately, helps manage this very sticky two-sided tape.

It's not unlike the stuff you'll see used to affix magazine inserts - you can wad it up to fill a spot, or lay it out thin and flat like a double stick tape.

[Possum]

cool idea.....

does this stuff interact with nickel like silicone does? or mar plastic?

[Dave Kerr]

It's low acid or acid-free, iirc - it's sometimes used to splice film, so I'd expect it would be pretty inert.
edit - some, not all, atg tapes are acid and solvent free.