Grounding Issue?

Discussion in 'Pickups & Electronics [BG]' started by MothBox, Dec 30, 2013.


  1. MothBox

    MothBox

    Joined:
    Oct 25, 2010
    I've finished rewiring my bass and grounded everything (I think). There's wires from the bridge which I connected to the other grounds and then grounded the lot to the plug on the jack. I didn't connect this ground to the output lug however (as had been done before).

    I'm using a pair of VOX amPhones and have no problems however when I plug my laptop into the headphones alongside my bass when I touch the strings I get a lot of noise (fuzzy hiss) through the phones. Is this related to grounding?

    This does not happen when my ipod is plugged in, only when the laptop is.

    Not sure if its related to the laptop creating some sort of circuit or if its poor grounding in my circuitry.

    Something else I've just noticed is that when the tone pot is open (i.e. no cap) there is a really faint hiss, when it is closed there is no noise at all.
     
  2. Wolffgang

    Wolffgang

    Joined:
    Jan 1, 2012
    Location:
    Newcastle, Australia
    If I'm understanding you correctly, yes it's a grounding issue. I don't know enough about electronics (or anything >.>) to tell you why, but I know when I mentioned having the problem to a local music store owner years ago, he told me to buy a double-adapter, open it up and remove the ground pin and plug into that before the wall, and it worked. That said, I've had two subsequent laptops and a desktop that haven't had that problem, so I've no idea why it happened.
     
  3. MothBox

    MothBox

    Joined:
    Oct 25, 2010
    Noticed some advice on guitar grounding says that if I wire the bridge into the grounding circuit I will notice buzz which goes away when I touch the strings. It may be that as I wired the whole lot together. Surely if I wire the bridge and the circuit to the grounding lug on the jack it will form a circuit anyway and that's the only true way to ground the instrument?
     
  4. ex-tension

    ex-tension

    Joined:
    Jun 11, 2009
    Probably it's related to the laptop's charger. Some of them cause this kind of noise.
    Connect your laptop to your amPhone without charger and see is this the case.
     
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  6. uOpt

    uOpt Supporting Member

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    Location:
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    I got a parse error on this one.
     
  7. MothBox

    MothBox

    Joined:
    Oct 25, 2010
    I'm not saying its not grounded, Its grounded to the ground lug on the jack. However previously the output lug of the jack was also grounded to the ground lug of the jack. I thought this may cause some signal decay as output "sound" may travel along the grounded section.

    Its a stereo jack but I'm only connected to the left side.

    First time wiring up my bass so its a learning curve.
     
  8. aphexafx

    aphexafx A mind is a terrible thing. Supporting Member

    Joined:
    Dec 10, 2013
    Location:
    Denver, Colorado
    Well I thought I understood what you were saying but now I'm more confused. If the instrument was outputting a signal originally then the signal (tip) was never connected to the common/ground (sleeve) on the output jack. I'm guessing that you saw a jumper from the sleeve to the ring or a jumper from an integrated switch to the sleeve. But those are just guesses. Why does it have a TRS (stereo) jack? Was it active or did it have an external PS or ???

    Perhaps you should just post a pic. :p

    Regarding the faint hiss: every signal has a noise floor and if its up there then rolling back your tone will affect how it sounds just like it affects how your signal sounds. A typical tone circuit will usually start to filter out (quiet) whatever floor hiss you have as u engage it. That's normal.

    As to ground wiring: yes, connecting your bridge ground to a joint ground point is fine as long as that ground point is connected to the common/ground lug of your output jack eventually.
     
  9. uOpt

    uOpt Supporting Member

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    Jul 21, 2008
    Location:
    Boston, MA, USA
    You don't have to connect the ring lug in the output plug.

    Just bunch all the mass cables together.
     
  10. MothBox

    MothBox

    Joined:
    Oct 25, 2010
    Thanks, it was an active setup before with a neutrik stereo output jack. I think ill have a look at the ground wiring from bridge to make sure its all connected properly.
     
  11. MothBox

    MothBox

    Joined:
    Oct 25, 2010
    This is the jack. My soldering isnt the best.

    Im tempted to shield the control chamber with copper shielding, i think the black paint is some sort of shielding paint.
     

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  12. uOpt

    uOpt Supporting Member

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    If the paint is conductive paint it needs to be grounded to act as a shield.

    I still have no idea what you are trying to say about the plug lugs, man :)
     
  13. MothBox

    MothBox

    Joined:
    Oct 25, 2010
    Initially the active electronics were setup with a left, right and a ground on the output jack.

    Then I had it passively wired in a shop and the left lug (output) was wired with the central lug being wired as earth. Then the left and earth were also wired together.

    I've not done that as it seemed strange to me to wire the output lug and the earth lug together.

    Just above someones commented that the output and ground lugs don't need to be connected so I'm leaving it for now. I just wondered why this had been done in the first place and if it was to do with the mild noise I'm getting.

    Once I redo the wiring I'm going to look at copper shielding the whole thing and properly the pickup cavities too.
     
  14. aphexafx

    aphexafx A mind is a terrible thing. Supporting Member

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    Well it looks like you have a unswitched stereo Neutrik jack in there so often when using a TRS (stereo) jack for a mono signal, the ring and sleeve are wired together because they both occupy the space of the sleeve on a proper TS (mono) jack. This isn't required on a jack because as long as the sleeve is in contact it doesn't matter that the ring is floating. However, sometimes this is used as a switch because inserting a TS (mono) plug will close a circuit between the sleeve and the ring which can be used to control power to a preamp.

    But what it comes down to, if I understand, is that you have a now passive instrument so all you need to make sure of is:

    1) The signal from your volume pot (or wherever it comes from) is connected to the Tip lug of your jack.
    2) The ground(s) is connected to the Sleeve lug of your jack.
    3) The Tip lug of your jack is NOT connected to the Ring or the Sleeve lugs of your jack.

    You may leave the Ring lug floating; it grounds when u insert a plug anyway.

    Note: If you connect the signal (what you call output?) lug (Tip) to the ground lug (Sleeve) you will mute your instrument, and this is exactly what MOST volume pots are doing when at zero volume.

    What is confusing is your use of "left, right, central" terminology tho.
     
  15. MothBox

    MothBox

    Joined:
    Oct 25, 2010
    Thanks for your info.

    Its just because I don't know the terms, so looking at it with the ring lug at the bottom I wired the signal to the left lug (tip) and the ground to the central/lower lug (sleeve) and left the right lug empty (a 2nd tip for stereo I assume).

    Previously the tip and sleeve lugs... if this is infact what they are, were wired together and this didn't cause any signal problems. Does this imply there is something different going on here?

    To be honest I'd be happy to replace the jack as the locking system annoys me but its a square plate and I don't want random holes so I'd need to make a little control plate to cover that area to install a normal jack. Or break the plastic locker I suppose.
     
  16. RobbieK

    RobbieK

    Joined:
    Jun 14, 2003
    Did you try Extension's advice? Laptop chargers are notorious for this sort of thing. My home studio is based around a laptop and I use an after market charger that has no mains earth.
     
  17. Marley's Ghost

    Marley's Ghost Supporting Member

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    Feb 9, 2002
    Location:
    Delawhere
    I use an isolation transformer from radio shack. Takes care of the laptop ground issue for $17.99.
     
  18. MothBox

    MothBox

    Joined:
    Oct 25, 2010
    My laptop has a plastic earth in the plug (UK style mains plug). I've always thought these were a bit strange as this doesn't earth the plug itself. Its an old piece of kit that I'm not willing to spend money on.

    Usually I plug my ipod into the amPhones so have little problem although there is still a bit of noise when using the tone pot, not audible through an amp but through the amPhones I can hear a lot more.
     
  19. MothBox

    MothBox

    Joined:
    Oct 25, 2010
    Similar sort of thing I noticed a huge amount of noise using a pedal plugged into the mains. When it was running on a battery there was no problem. Swapped the plug for a one with a proper metal grounding and there were no problems at all.

    I'm not sure if this problem is occurring as a result of my circuitry or not because I've not had this problem before.
     
  20. RobbieK

    RobbieK

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    Jun 14, 2003
    so there's no noise when the laptop is on the battery?
     
  21. MothBox

    MothBox

    Joined:
    Oct 25, 2010
    when the laptop is running on battery noise gets louder - the opposite to what I expected.

    Used a unmodded P-bass, no problems at all. So I'm definitely putting the problem with my wiring or grounding.

    I haven't grounded the blend pot but I don't think that will of had any major effect.

    The plug I changed was for an FX pedal. That seems to of resulted in a grounding of the circuit when playing so this may act as a temporary fix but I'd like to get to the root of the problem with the wiring or pickups.
     

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