Grateful Dead Music Forum

A place to talk about the music of the Grateful Dead 

 #124648  by mkaufman
 Mon Feb 18, 2013 1:20 pm
I have a guitar which has two pickups right next to each other. When either pickup is turned on, I can tap on the other pickup and hear sound. As I move the pickups away from each other, the sound picked up from the other pickup lessens. At about 1.5" inches away, the sound is no more.

So, it seems that the magnet from one pickup is picking up from the neighboring pickups coil. Ultimately, I'm not sure how much 'bleed' there is, however, I'd like to know if it's possible to place a thin strip of material between the pickups which will stop this from happening and not impact the sound of either pickup?

 #124653  by gmchart
 Mon Feb 18, 2013 1:58 pm
Maybe the other pup being so close is a red herring. Tap within an inch of the activated pup but on the other side (away from the other pup) and my guess is you'll hear it too. Vibration is vibration, from a string or a finger.
 #124660  by mkaufman
 Mon Feb 18, 2013 7:06 pm
You nailed it. My assumption was wrong. Turns out that the pickup is just picking up the vibration of the tap and amplifying it. As the pickups are moved farther away, there is less vibration from tapping. Even tapping ever so slightly on the body produces a sound. The pickups are quite sensitive!

This also explains another observation: when using a coil cut on a humbucker, one coil is cut out of the circuit resulting in a single coil pickup. In order to identify which coil is cut and which remains, one should tap above each coil to determine which coil is still active. In my experience (ie: with an Ibanez Super 80 trisound pickup), I hear sound regardless of where I tap to make noise. I suspect the same thing is happening: the active coil is just picking up the vibration. So, this has never really worked for me. Maybe it would work without a pickup cover.

 #124661  by gmchart
 Mon Feb 18, 2013 7:27 pm
I use my watch. Needs to be analog (tick tock). Hold it above the strings and move it back and forth. Takes a bit of trial and error but you can figure it out.