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Ok, this has to be a shielding problem

Discussion in 'Hardware, Setup & Repair [BG]' started by Smokey, Mar 21, 2004.


  1. Well, I have read many posts of people who have this problem, but I haven't found any one solution, just many opinions. When I play my bass through my bassman 60, I get a loud buzz/hum, which gets louder as I increase volume. This hum goes away if: I turn the tone control all the way down on my bass (MIM Fender Precision), or if I touch something metal on the bass (bridge, volume/tuning knobs, strings, etc) It gets Much louder if I stand near a turned on TV or PC. Is this the result of a bad ground wire near the bridge, or something else? I could always take it to the local dealer, but I would like to hear some of your opinions or past experiances with this. Any input if appreciated.
     
  2. It's very likely a shielding problem. My old bass had the same problem.
     
  3. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    I ground wire to the strings might help a bit. Picking up noise around TV's is common with ANY bass. Shielding will probably help a lot of the noise that dissappears when you touch the strings.
     
  4. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    If you have a multimeter, you can find out whether the ground wire to the bridge is connected properly. Using the low ohm scale on the meter, measure between the sleeve of the jack and the bridge, if you read zero ohms it's continuous and the wire is connected properly.

    There's a lot more to these hum problems than meets the eye. Sometimes a bit of shielding will fix the problem, sometimes it'll make it even worse. Does your bass behave the same way with other amps? Sometimes the problem can be in the amp itself, even though the symptoms only appear when you touch the strings.

    I only know of one surefire 100% certain way to get rid of the hum in passive basses, and that's to add an onboard differential input active preamp. It has to be the right kind though, most of the preamps being sold "aren't", and may or may not fix a hum problem.

    You might want to check the "guitar wiring" menu on guitarnuts.com, there's a lot of good information on there (especially the part about "star grounding").
     
  5. dTune

    dTune

    Feb 28, 2004
    Finland
    I've noted the same problem, but only on Fender amps... Don't know if fender uses a component that messes up the grounding or what, but i've never experienced it (at least not as bad) on any other amp makes. It's weird.

    BTW, it has to be a grounding problem ore closely related to grounding, otherwise the buzz wouldn't probably stop when touched.
     
  6. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    Don't do Fenders but a Bassman 60 doesn't sound like monster. I'd grab a fat (like construction grade) extension chord and run it to the middle of nowhere (farthest possible from mankind's stuff - and power lines) and fire it up and see what happens. Then at least you know you're dealing with the bass and the amp - unless you live in an old house without third wire grounds.
     
  7. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    Smoke'n'Mirrors, try going to a friends house and playing there. You could be getting hum from the house or the electrical system. I bought an amp that I had to take back due to the excessive hum. It worked great at the store, worked great at my parents, hummed like crazy at my house. Yet other amps in the same location have no problem at all.

    Some tests:
    • Is there hum if the bass is disconnected?
    • If no, plug in a cable (with no bass). Is there hum?
    • If no, then it could be your bass.
     
  8. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    One thing I've learned though, anytime I think anything has to be something in particular, I'm pretty much wrong.
     
  9. There was no hum when I turned it on without the bass plugged in. The only other amp I have to test my bass on a rogue 20 watt, if it is in fact the bass, will I get the same hum from this smaller amp?

    Edit: Ok, I checked. I got the same electronic hum from the rogue as I got from the bassman. Is it safe to assume it's my bass doing this?
     
  10. I'd be thinking it is a problem with the bass, perhaps shielding as you've suggested. If there's any way you could find another bass or guitar to test on your amp(s), plugged into YOUR AC outlets, then this would rule out the possibility of AC electrical wiring problems, etc.. Then at least you'd know it was the bass.
    Of if you could take the bass and amp to a music shop, test it to see if it hums there, and then try a few other instruments..

    I'm getting hum like this on an el cheapo Rogue bass guitar that I'm working on. It has split pickups, and no shielding on any of the wiring.

    Mag...
     
  11. bassmantele

    bassmantele

    Jul 22, 2003
    Boston MA USA
    The buzz you get is normal for non-shielded instruments. When you touch any grounded metal part - including the strings - the buzz goes away. The bridge is grounded in order to give you the silencing effect when you touch the strings - that's a good thing, as far as it goes. Go to guitarnuts.com and read up on shielding - there's a great how-to there that should get rid of the buzz.