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Why would a bass suddenly start buzzing?

#44
grendle said:
True, what I was referring to is minimal wire length with minimal connections. Emg, no ground wires no buzz ;)
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Minimal wire length is good. Minimal connections means nothing. You can't have ground loops in a single grounded system like a bass.

EMGs have ground wires just like regular pickups, they just don't ground the strings because they don't need it.

EMGs are quiet because they are fully shielded, unlike most other pickups. They also use a differential connection to the op amp, which helps reduce noise because they are balanced.
 
#45
The pots and output jack will be connected through ground just by being fixed to the copper shield, if you go ahead and add extra ground cables you will just be creating potential ground loops which will cause buzz. You don't even need to connect the shielding to ground as the output jack's frame itself is connected to the ground in your guitar lead. To have minimal noise you should have coax cables connecting your hot signals and no ground cables at all (check to make sure all pots are grounded through the shield) Every point should have only one way to reach ground (except for signal wires, which shouldn't be grounded).

If you touch something and noise goes away it means you touched something that is grounded, as your body acts as an EMF shield when it is grounded.
 
#46
Keplaffintech said:
The pots and output jack will be connected through ground just by being fixed to the copper shield, if you go ahead and add extra ground cables you will just be creating potential ground loops which will cause buzz. You don't even need to connect the shielding to ground as the output jack's frame itself is connected to the ground in your guitar lead. To have minimal noise you should have coax cables connecting your hot signals and no ground cables at all (check to make sure all pots are grounded through the shield) Every point should have only one way to reach ground (except for signal wires, which shouldn't be grounded).

If you touch something and noise goes away it means you touched something that is grounded, as your body acts as an EMF shield when it is grounded.
Click to expand...

You can't have a ground loop in the bass because you only have a single ground. Ground loops are caused when you have two ground circuits connected together with different potentials. Since the bass has a single ground at the output jack, you have a single potential in the circuit. All grounded points in the bass are at the same ground potential.

The small resistances of the wires are inconsequential, and having multiple grounds reduces the resistance because they are in parallel. Also all the voltages and currents are very low.

This is one of those instances where what's true in theory is not true in practice, and doesn't apply here.

The problem with the pots touching the copper is that copper oxidizes and the connection will be compromised over time.

The shielding must be grounded. Your jack is grounded, but the shielding must be connected to that, otherwise it is floating.

This is how Bourns says to ground a guitar. They are using the standard daisy chaining method:

http://www.bourns.com/data/global/pdfs/bourns_82_and_95_grounding_appnote.pdf

PROPER_GROUND_PROCEDURE.png
 
#47
SGD Lutherie said:
Minimal wire length is good. Minimal connections means nothing. You can't have ground loops in a single grounded system like a bass.

EMGs have ground wires just like regular pickups, they just don't ground the strings because they don't need it.

EMGs are quiet because they are fully shielded, unlike most other pickups. They also use a differential connection to the op amp, which helps reduce noise because they are balanced.
Click to expand...

minimal connections give less to go wrong (murphy's law, he rules everywhere) . I agree with you in general on everything else. The OP has a setup with everything running a ground wire to a central lug which is grounded. I have had and seen issues with this type of wiring is all I was saying. Imo as in the link you posted, in my experience grounding each component to each other then running a single ground wire to the bridge is best.

Nice pickups BTW
 
#48
grendle said:
minimal connections give less to go wrong (murphy's law, he rules everywhere) . I agree with you in general on everything else. The OP has a setup with everything running a ground wire to a central lug which is grounded. I have had and seen issues with this type of wiring is all I was saying. Imo as in the link you posted, in my experience grounding each component to each other then running a single ground wire to the bridge is best.
Click to expand...

Agree 100%! That star grounding method usually leads to more problems than it solves. You need it in tube amps, but not guitars.


Nice pickups BTW
Click to expand...

Thanks!
 
#49
I guess it's bittersweet that the legwork I did before the thread was confirmed in the thread.

So, off to a new pre I see. Not that I disliked the OBP-1, but I'm looking for more control than a two band, boost only set up.

Any suggestions?
 
#50
SGD Lutherie said:
Ground wires don't cause buzzes. Lack of ground wires causes buzzes.
Click to expand...

Boy are you ever right.

As I was sitting in my living room, I noticed where a ground lift had been used to plug in the TV because there was not a 3 prong outlet. Then I remembered that I had changed all the outlets in my bedroom to 3 prong outlets even though they weren't grounded. I simply needed them to accept those types of plugs.

Then I remembered I had never had my amp at my house (until recently, it had been at a church exclusively. I'm not longer at that church and my gear is here now though my amp had been at the Mesa headquarters being serviced so I don't correlate it to being a new place because the rest had been here for some time).

So I plug the bass back in, buzzing like mad and I touch the chassis of the amp. The buzz decreases. I find one of those ground lifts for the outlets, run an external ground and the buzz disappears. Entirely. Completely. It was never the bass, pre, grounding of the bass, cab, amp. It has been my house the entire time.

I suppose the other two basses did not buzz due to the EMG pickups in them? I thought the testing with the others basses had eliminated any possibilities not exclusive to my LeCompte, but I suppose they were poor testing basses in hindsight.

So tl;dr, my bass doesn't buzz. My house does. My pre amp is fine. I'm having major mixed emotions of relief and infuriation. :rollno:

Thanks to all the help I received anyway! :)
 

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