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annoying hum when not touching the strings

Discussion in 'Hardware, Setup & Repair [BG]' started by dolphin_wank, Apr 24, 2006.

  1. when im not touching the strings on my bass i get a high pitched hiss coming out of my amp

    the obvious reasoning is grounding, but the plug socket is grounded (earthed, standard in UK plugs), i've tried a couple of different 'kettle' leads going into the amp, but the bass still hisses with all of them

    i'm using an ashdown mag300 combo amp

    i don't recall this happening before, and i swopped the neck over today from a fretted to fretless, dunno if this has anything to do with it.. doubt it.

    any ideas anyone?

    this is probrably the most asked question on this forum ever, but oh well.

    cheers in advance
  2. vene-nemesis

    vene-nemesis Banned

    Jul 17, 2003
    Bilbao España
    Get hum canceling pickups.
  3. i was sort of hoping for a cheap, or better yet, free option :bawl:
  4. vene-nemesis

    vene-nemesis Banned

    Jul 17, 2003
    Bilbao España
    Start praying and you might get your miracle.
  5. i think you're missing my point here

    it wasn't doing it before

    it is now

    i'm confused.

    if it wasn't doing it before, then surely i don't need noiseless pickups, all i need is someone to suggest some troubleshooting ideas
  6. vene-nemesis

    vene-nemesis Banned

    Jul 17, 2003
    Bilbao España
    Dude, if your pickups aint humcancelling you bass will hum no matter how much you try to avoid it, how well shielded it is or if its gorunded or not this last one happends because basses usally use mono cables not gorunded ones...
  7. Juneau


    Jul 15, 2004
    Dallas, TX.
    But pickups dont go from silent to having a hum from changing out a neck. Your suggesting something that has no relevance to his situation. His pickups didn't hum when he had a fretted neck on, and now, with a fretless neck they do. Its obviously a grounding or shielding issue (i would bet grounding - as your hand touching the strings grounds it - and it might not be the jack). I wouldnt know where to begin on troubleshooting though personally. Perhaps some of those more adept at electronics can provide him with some usefull suggestions.
  8. Dan1099

    Dan1099 Dumbing My Process Down

    Aug 7, 2004
    Your bass either has no shielding, or or it's shielding is no longer corrected to ground.
  9. this might sound retarded, but what is shielding?

    i'm absolutely clueless about electronics
  10. Juneau


    Jul 15, 2004
    Dallas, TX.
    That foil looking crap thats inside your electronics cavity and underneath your pickups. From what I gather above, its supposed to be attached to the ground wire that connects under your bridge.
  11. ah, right.

    interestingly enough its stopped doing it temporarily now.

    odd. :/
  12. Juneau


    Jul 15, 2004
    Dallas, TX.
    You prolly just knocked something loose thats not staying as connected as it should. I would just open it up, make sure everything is secure. I believe you can just glue down the shielding, and of course solder any points that might have come loose. If your not comfortable doing that, Id take it someplace though.
  13. avid

    avid born lefty

    Jun 22, 2005
    Ashland, Oregon USA
    Saturday I went to practice and just about lost my mind trying to figure out where the hum was coming from. I finally isolated it down to my Fender Rumble with nothing else connected. I managed to move away from my amp about 10' and get a practice in. Sunday there was no hum. My impression is that my wireless network, usually off when I am practicing, my have been throwing some kind of interference that the Rumble was picking up.

    My other possible problem could be that I have a ground loop in my house. It has driven me to distraction with my computer sound system. I solved that problem by not grounding my computer. It seems to me the loop happens more during dry conditions. (and it finally quit raining here in the US PNW, hallelujah!)The issue is that I have separate grounds for my CATV and my house electrical system. The CATV company insists on a separate ground. Even if I wanted to combine them I have no idea where the ground is for my house. I suspect it's buried underneath my garage floor. Ground loop issues are tricky; look in google and you will see that audiophiles are big into solving them.


  14. The buzzing could also be the result of a non-conditioned power source.

    In short, your electricity flow might not be constant, and would probably be varied, or unfiltered.

    I get this buzz from my P-Bass, but not my fretless J-Bass. I highly doubt that swapping the necks would cause a grounding issue, unless you have some form of a ground wire or something that goes between the neck and the electronics.
  15. The first and most simple thing to try first: Turn the AC connector the other way around. Sometimes this wil solve the problem. One of the pins of this connector is for alternating + and - 110 volts. The other one is the 0. Somehow it can make a difference how you plug it in. Don't ask me the specifics. I'm no electrician.
  16. Turnaround

    Turnaround Commercial User

    May 6, 2004
    Toronto Canada
    Independent Instrument Technician, and Contractor to Club Bass and Guitar - Toronto
    Don't mean to be pedantic here, but it's not that you are grounding the bass when you touch the strings - you are grounding yourself. The bass is already grounded, but it is picking up electo-magnetic noise from your body which is acting like an antenna. When you touch the strings you ground yourself which drains the noise.

    Sorry - that useless bit of information doesn't help you with your problem though....:(
  17. Son of Magni

    Son of Magni

    May 10, 2005
    Builder: ThorBass
    Almost correct. Actually what's happening is that when you touch the strings you are grounding your body which causes your body to act as a shield. When you're not touching the strings, it's not that you're acting as an antenna, but just that you're not shielding the EMI.

    In any case, either the bass has a shielding problem or there is a new source of EMI in the area where you are playing and your wireless LAN is certainly a suspect.
  18. pkr2


    Apr 28, 2000
    coastal N.C.
    Just checked your profile to try to figure what brand and model bass you play. Not familiar with the gear that you list.

    If your bass is passive, the connection that grounds your bridge is likely to not be making a good connection.

    The wire that grounds the bridge is usually just squeezed between the bridge and the wood of the body. Not the best mechanical connection.

    You can easily check for the problem by connecting a temporary ground wire between the bridge and the nut that retains the output jack with a short piece of wire. No need to make a solid connection. Just touch the bridge with one end of the wire and the jack nut with the other end. Be sure not to be touching the bare wire with your fingers while testing. Hold the wire by the insulation.

    If the noise goes away, repair the connection, either under the bridge or in the cavity. .

    Disregard my suggestion if your bass is active. Active basses normally dont require that the bridge be grounded.
  19. hahah, i think i might do it seriously now that i've actually started posting here, thought i'd only post here once or twice

    really good advice tho man, thanks, i'll try that now :ninja:

    and yeah its a passive jazz bass
  20. Turnaround

    Turnaround Commercial User

    May 6, 2004
    Toronto Canada
    Independent Instrument Technician, and Contractor to Club Bass and Guitar - Toronto
    Thanks for that. Bit of both I suspect. For instance, if I grab the hot end of a lead that's plugged into an amp, I introduce audible noise. But as soon as I touch the grounded side, the noise is drained to ground. Unless I am missing something, it's my body introducing noise. But for sure I can see that grounding myself will effectively cause my body to be a shield. Funny though how many people think you are grounding the instrument when you touch the strings.

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