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Buzz when not touching strings

S

Scott549

Oct 26, 2009
427
11
Madison, Wisconsin
www.willsband.net
#1
I'm getting a mid-high frequency buzz when I take my left hand off the strings of my Jazz bass. I assume this is some sort of grounding problem. I recently replaced the pickups with the help of a friend who knew what he was doing. We're pretty sure we got it grounded properly but my friend is wondering whether there might be an issue with the ground to the bridge. I also replaced the bridge recently and there was an exposed wire under the old bridge that I am pretty sure was in good contact with the new bridge when I installed it.

Any ideas on this?

Thanks.
 
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#2
Scott549 said:
I'm getting a mid-high frequency buzz when I take my left hand off the strings of my Jazz bass. I assume this is some sort of grounding problem. I recently replaced the pickups with the help of a friend who knew what he was doing. We're pretty sure we got it grounded properly but my friend is wondering whether there might be an issue with the ground to the bridge. I also replaced the bridge recently and there was an exposed wire under the old bridge that I am pretty sure was in good contact with the new bridge when I installed it.

Any ideas on this?

Thanks.
Click to expand...

It means the bass wiring needs to be shielded or the shielding that's there is not properly grounded. Since touching the strings makes the buzz go away that says that the bridge is indeed properly grounded. (you can test it with a meter)

Does your bass have shielding? If not one possibility is that the new pickups use unshielded wires while the originals used shielded wires. Hence the new wires will pick up hum.
 
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#4
If the buzz goes away when you touch the strings, the ground wire to the bridge is fine. Buzz is a (lack of) shielding issue. You can buy shielding tape or electrically conductive paint to line the pickup and electronics cavities of the bass.

Semi-OT: Jack Read pointed out many years ago in email to The Bottom Line list (showing my age here!) that a ground wire can result in shocks if you have a power grounding issue. He uses (used?) a .001uF/500V cap in parallel with a 220K resistor between ground and the bridge to bypass high frequencies while leaving enough resistance at power line frequency to avoid serious shocks. I really need to upgrade all my instruments to this...
 
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#6
lawnranger said:
I have the same problem, buzzing that goes away when I touch the strings. Can someone explain to me what shielding is and does it have a "home" remedy? Thanks! Wayne
Click to expand...

I got my info from "Quieting the Beast" over at guitarnuts (including the isolation cap approach). Basically YOU are an antenna -- you collect noise, and channel it right by your bass, its electronics, etc. That noise gets to your amp and is amplified -- hum. When you touch the strings, if the ground wire is in place, you shunt all that noise to ground, and thus it doesn't get amplified.

Shielding goes like this:

You create a metal box around your electronics, and connect that metal box to your ground wire. Now, any noise that tries to get into your signal first hits that box, and then is immediately shunted to ground. So, as long as you have a nice complete box of metal around your electronics, and have it connected to ground, you're all set. I use the copper tape for my favorite instruments, conductive paint if I don't have the tape around, and I've even used tin foil for some beaters...got plenty good results. It's not as clean or slick looking, but it's economical as hell lol ...so that's your home remedy. (you can't solder to it, so to connect the ground wire to the shielding, I put the wire around a wood screw and screw that through the foil at some place where there's a lot of wood for it to bite into...again, I don't go this route unless it's a beater)
 
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#9
We did the shielding project with the Jazz bass today. Basically coated the electronics compartment and covered the wires to the pickups with heat-resistant metal tape. It is now substantially better, probably a 70 percent reduction in the noise when not touching the strings.

I do wonder why the Precision has no such issues, though. It is very quiet all the time.
 
#11
Even when you shield and wire to ground properly the buzz will be still there. I remember recording sesions years ago that i got to wire a cable from de bass to myself to avoid the buzz. The best is to buy shielded pickups, EMG, Bartolini or some high end pup, they dont buzz at all. A serious pup should be shielded or casted in epoxy, if not, i believe its so cheap, prehistoric design...
 
#13
Hi all,

I have a slightly different issue on my P/J.
I get a high pitch hiss/buzz when I have the Tone turned up and noth P/J volumes at 0. It worse when I put the P volume up and gets 3 x worse when I turn up the J.
It comes and goes, if I leave the bass on its stand the buzzing comes and goes.
Would this be a grounding issue?
Thanks
Daniel
 
#14
RambleOn said:
Hi all,

I have a slightly different issue on my P/J.
I get a high pitch hiss/buzz when I have the Tone turned up and noth P/J volumes at 0. It worse when I put the P volume up and gets 3 x worse when I turn up the J.
It comes and goes, if I leave the bass on its stand the buzzing comes and goes.
Would this be a grounding issue?
Thanks
Daniel
Click to expand...

Have you eliminated the amp and cords as possible cuplrits? And does touching the strings impact the noise level?
 
#15
lethargytartare said:
Have you eliminated the amp and cords as possible cuplrits? And does touching the strings impact the noise level?
Click to expand...

It has happened with two different amps and two different cords. Touching the strings reduces the noise level. As I said in my last post, this "noise when not touching the strings" has been significantly reduced since we installed all the shielding, but it's not completely gone and quiet like my Precision is.
 
#16
Scott549 said:
It has happened with two different amps and two different cords. Touching the strings reduces the noise level. As I said in my last post, this "noise when not touching the strings" has been significantly reduced since we installed all the shielding, but it's not completely gone and quiet like my Precision is.
Click to expand...

I was actually replying to RambleOn -- sorry for the confusion there!
 
#17
lethargytartare said:
Have you eliminated the amp and cords as possible cuplrits? And does touching the strings impact the noise level?
Click to expand...

Touching the strings reduces the hiss but nut the buzzing. The cords have been ruled out since I've used different ones...not the amp. What surprises me is that it does this with the P (the J is SC so I would expect noice, maybe not so much but...) however when the tone is down, it's fine...
.
 
#18
RambleOn said:
Touching the strings reduces the hiss but nut the buzzing. The cords have been ruled out since I've used different ones...not the amp. What surprises me is that it does this with the P (the J is SC so I would expect noice, maybe not so much but...) however when the tone is down, it's fine...
.
Click to expand...

The tone thing is actually not surprising -- most hiss and buzz have a lot of high frequencies in them, so cutting treble makes them seem to go away. If you had a treble boost circuit, you could probably make it dramatically worse still!

So if touching the strings reduces some of the noise, but the buzzing keeps constant, I'd start to suspect something in the circuitry (again, assuming I had ruled out amp and cables).

And this doesn't have active electronics, does it?

If you're handy with a soldering iron, you can try scaling down the wiring to just the P and a volume control and see what you get. Be sure to double check basic stuff like the output jack, any obviously frayed or barely attached wires, etc.
 
#19
lethargytartare said:
The tone thing is actually not surprising -- most hiss and buzz have a lot of high frequencies in them, so cutting treble makes them seem to go away. If you had a treble boost circuit, you could probably make it dramatically worse still!

So if touching the strings reduces some of the noise, but the buzzing keeps constant, I'd start to suspect something in the circuitry (again, assuming I had ruled out amp and cables).

And this doesn't have active electronics, does it?

If you're handy with a soldering iron, you can try scaling down the wiring to just the P and a volume control and see what you get. Be sure to double check basic stuff like the output jack, any obviously frayed or barely attached wires, etc.
Click to expand...

It's passive. Output Jack...hadn't considered that! Looks like I'll have no choice but to carefully go through all the wiring.
Thanks
 
#20
RambleOn said:
It's passive. Output Jack...hadn't considered that! Looks like I'll have no choice but to carefully go through all the wiring.
Thanks
Click to expand...

Yeah, it stinks, but it's also a good time to reshield -- take everything out, shield it, add in just a volume and one pickup, test. Add in the pan pot (or second volume), retest.

If you're redoing it all and shielding, it is much easier to track your progress as you rebuild step by step than if you are leaving everything in and disconnecting things and trying to diagnose that way. Plus, if you find a bad part, it's easier to replace at that time, etc....still a bit tedious.

good luck man!

ltt
 

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