got that hum!!

Discussion in 'Pickups & Electronics [BG]' started by tyburn, Feb 17, 2001.

  1. got a hum guys!!,, got some new pu's fitted in the beats ( j bass) and love it.. the only problem is that from time to time i get ahum and ofcourse it stops when i touch any metal part of the bass and ground it

    how do i get rid of it,, sheilding the cavity,, the earths are all ok ,, well they were,, it comes and goes, some days are worse than others,, some not at all

    i suspect that the power supply is "dirty" as i would describe it , cos it happens to my brothers guitar amp when he plugs it into the same socket

    any ideas
  2. Sounds like the 120VAC outlet is wired backwards, i.e. hot and neutral are reversed. If your amp doesn't do this in another 120VAC plug, then this is probably it. Old amps with 2 prong plugs have a polarity switch to "fix" this. Get an outlet checker at the hardware store to check the outlet's wiring. Don't mess with it if you don't know what I'm talking about. It's probably not your bass's fault.

  3. thing is i know that the sockets fine cos my dad built the house!!,, and it's bee wired correctly for 12 years

    i live in england so we've got 240v

    would it be worth sheilding the control cavity?
  4. My bad, should have checked the profile to see your location.

    Still, if you plug into another outlet in the same house or another outlet in another building, does it go away? If it does go away when plugged into another outlet, I'd suspect the outlet. If not, I'd suspect the amp. Of course I'd swap instrument cords and power cords at some point to rule that out, too. The bass would be the last thing I'd suspect, but I've been wrong before.....

  5. rickbass

    rickbass Supporting Member

    Two big sources of hum/buzz are AC electrostatic fields and electromagnetic fields which come from lighting dimmers, electrical wires, fluorescent lights transformers, power transformers in amps, your PC, et al. Pickup coils and unshielded wiring can actas antennae and pick up these fields and introduce them into your signal.

    Electromagnetic shows up as 60Hz hum, close to Bflat. It will grow/disappear ass you turn the bass toward/away from any hum sources such as your amp. the only way to get rid of this type is with humbuckers.

    Electrostactic is a buzz. It's a buzz you hear when you take your fingers off the strings. It can be eliminated through complete shielding of the pups and the control cavity. If the shielding on your bass, (assuming there is shielding), isn't connected to ground, the shielding is turned into a big hum magnet. Some basses are built this way for whatever reason, (e.g., poor workmanship, et al).

    Oh yeah, you said a "j bass." When you have both turned up does the hum go away? Both of the single coil pickups act as a humbucker when you turn them both up.
  6. from what u've pointed out rickbass1 it sounds as if i've got electrostatic hum,, i've got dimarzio ultra j bass pu's fitted and there fine,, i've got no sheilding to my knowledge,, thats why i thought about doin it,,,

    i have a rough idea on how to do it,, but what would it cost to geta tech to do it ??
  7. Do active pups like EMGs or the Duncan active EQ range suffer from electrostatic hum?