What exactly is "phase"?

Discussion in 'Pickups & Electronics [BG]' started by Nick Gann, Nov 30, 2003.

  1. Nick Gann

    Nick Gann Talkbass' Tubist in Residence

    Mar 24, 2002
    Silver Spring, MD
    I did a quick search and couldn't find what I was relaly looking for. I found plenty of "this is out of phase", but not what it is or what causes it.

    So, what does it mean if two pickups are out of phase? What causes it physically, and what does it sound like?
  2. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    Phase is described as "the stage of progress in a regularly recurring motion or cyclic process (as a wave or vibration) in relation to a reference point" (cf. Webster's dictionary).
    The string motion is something like that. The pickup turns this into an AC signal, which looks like sinus waves on a scope.

    If you compare two signals from two pickups and they boths move the same way (both in the +V range or in the -V range at the same time, they're in phase.

    When one signal is in the +V range and the other in the -V range, they're out of phase, and they partially cancel each other out.
  3. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Like JMX wrote...

    Out of phase connections can happen when the + or "hot" lead of one pickup is connected to the - or ground lead of the other (and vice versa). The overall sound is hollow with weak lows.

    Depending on how the pickup's magnet is oriented, it may be necessary to connect the pickup's leads backwards to actually have it in phase. This is particularly true when mixing brands of pickups (as I found out when installing a DiMarzio Will Power middle in my former Fender Am HR P with stock Fender bridge pup).

    I suppose that a pair of pickups could be connected in phase, but sound out of phase if they were installed at particular points along the length of the string. Kind of like how a Jazz Bass will sound with both pups at equal volume settings.