Unwanted Harmanics and Hum

Discussion in 'Hardware, Setup & Repair [BG]' started by nochoke, Dec 2, 2000.

  1. nochoke


    Dec 2, 2000
    Hi folks. This is my first post on this board, so please don't call me an idiot or anything if I put this in the wrong place or do something similarly stupid.

    I have two problems with my bass (fretted 99 Carvin B4 with a maple neck and koa body) and would like a little advice on what might solve them. It’s a passive, two pup setup with two volume pots and one tone pot. I'm not sure if the pups are the J99 single coil, or H50N stacked humbuckers. I have a very powerful and clean system and go for a tight, bright sound (600w into a 4x10 Hartke).

    My first problem is that when playing any open or lower register note on my E string, I hear other frequencies than the note I am playing. Since I’m not sure of the correct term for these phenomena, I refer to them as sub-harmonics. Damping the string gets rid of them, but then, you know what damping does to sustain… Right now I have a little piece of foam rubber between the bridge and the string which seems to work well (this is similar to many older basses that had rubber damping material lightly pressing against the strings). Doesn’t look too cool though, since there’s no bridge cover.

    The other problem is a hum (most likely 60 hz). This hum is noticeable when either of the volume controls is more open or closed than the other (this sort of defeats the purpose of having two pups eh?). I am not able to vary the pup’s signals since I have to have both of them always sending the same level of signal through. The hum gets worse when I increase the difference between the two volume pots (one all the way up and the other all the way down).

    I bought the bass at a Pawnshop, so it’s doubtful Carvin would be of much assistance. Actually, I sent them an email several months ago and to date have received no response. I really don’t want to sell it off to someone else, and it really is a beautiful, fine playing instrument.

    Any advice is appreciated.
  2. membranophone


    Mar 19, 2000
    Madison, WI
    This problem is typical of basses with single coil pickups. The two coils effectively create a humbucking pair when they are at the same level, that is why the noise gets greater as the difference in levels increases. You could reduce this noise with some shielding in the pickup cavities, or eliminate it by swapping the pickups with some stacked or split humbuckers.