• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

P-Bass Hum

Chef

Chef

In Memoriam
May 23, 2004
41,814
18,945
65
Columbia MO
Disclosures
Staff Reviewer; Bass Gear Magazine
#1
Generally, in a club with crummy electricity making any of my Jazzes hum, I can whip out a P bass, and, problem solved.

Last night, that was backwards.
Lakland P5 had wicked hum any time I took my hands off it, and I swear, I could almost feel it with my hands on.
I've never had this issue with this bass, and I've played that club plenty of times before.
This time I did not run my own extension cord, I got to the club late, just plugged into the splitter that powered that side of the stage, guitar player adn one Bose stick/sub.
I did try two different signal cables with same results.

Sadowsky Jazz, dead quiet, even with blend off center.

Tried it at home; same thing.
At home, amp is on a circuit that seems to have two light dimmers on it. Turn the lights off, all is quiet.
Same results with a different head and cab and cables.

I took the P5 down.
Bridge wire was sunk into the finish, this is common enough. Screwing the bridge down does that.
Moved it over to a fresh spot, made sure it was touching a mounting screw.

Same thing; pretty hummy with hands off.
Hands on, quiet.
Lights off, quiet.
Touch the amp, quiet.

Pop the p/g, clean the pots, make sure the ground from the bridge is secure on the pots (it is):
same results.

Running a test lead from the bridge to the pots does nothing to quiet anything.

What is this?

What can be done?
 
#3
You know I just had a MiM P bass here for a setup, and the owner also asked if I could check the wiring because it buzzed. Same deal as yours.

I did not have a lot of time with the bass, as the guy had a gig in an hour.

This bass had zero shielding. Not even foil under the controls. So I put some copper under the controls, and even some under the pickup. I also twisted the pickup's wires just for good measure. That didn't do a whole lot. It helped a little, but it still buzzed when I took my hands off the strings.

I noticed it buzzed more when I touched the pickup's pole pieces. This was one of those steel pole/ceramic magnet pickups. The one half was worst than the other, which was common.

I suspect that grounding the poles would have probably fixed the situation, that along with better shielding than I had time to do.

So, no real answer for you. How is the shielding in that bass?
 
#4
-both sides work, it sounds as great as it always has.
-it's a Nord NP5 pup
-there is zero shielding in there, shame on Lakland.

I have both copper foil and paint.
 
#6
buzz; hum: semantics?

I don't remember it behaving so very badly before at that club.
I have had basses be noisy on that circuit at home and sometimes I turn the lights off cause they bother me. Seems like this is generally a P bass issue at home, and I have pulled bridges and moved ground wires on P basses before, at home, trying to cure them.
So: that's a repeatable issue at home.

I don't know why things were so filthy at the club last night.
 
#7
I had a similar problem w/ my Glaub. I couldn't figure it out either, becasue everything looked as it should, so I took it to my tech. He ended up replacing the solid core wiring with braided wiring, because the solid core was so inflexible that it broke at a pot terminal, due to the forces of plugging/unplugging it through the years. There wasn't much slack in the original wiring as well. It was very hard to see the break, but I watched him find the problem, replace the wiring, and now it sounds as it should.
I don't know if your P has siminlar wiring, but it might be worth looking into. Good luck.
 
#8
Dmusic: if you can decribe what you mean the diff b/t buzz and hum to be, I could try to answer that better.

The ground wire from bridge to output jack is braided; and all the connections throughout the harness at least look and feel sound. I could re-heat all those joints again...
 
#9
Maybe the club's power was just a little more messy last night and it exacerbated the issue?

My active MIM PJ has the same issue as your bass and it bothers me enough that I haven't played it much recently. I'd suspect shielding would help out in my case. I've only been fortunate enough to have one rather quiet P-my Highway 1 with a J Worrell P and otherwise stock wiring. I twisted and trimmed down the leads and I think it has shielding on the back of pickguard from the factory.
 
#11
Chef said:
buzz; hum: semantics?
Click to expand...

Hum is the 60/120 Hz stuff you get from single coils. It doesn't go away when you touch the strings. It's caused by magnetic field interference. Humbuckers get rid of hum. Twisting leads helps with hum also.

Buzz is that high pitched electrical field noise. Humbuckers, such as the P bass pickup, can't get rid of buzz. Shielding fixes that.

When you touch the strings you are grounding your body, and becoming part of the shielding.
 
#14
My 64 P bass hummed. I changed the pickup in the late 70's. Later, I measured the original pickup and found one half was higher resistance. One half was either underwound or overwound. Had I just removed enough windings on the overwound half, the pickup would have been fine. Who knew back then?
 
#16
Chef said:
Sure.
From three rooms away, I can't hear it at all...

????
Click to expand...

Ha, I meant, while you're wearing the bass... if you push it away from your body, does the buzzing get quieter? I'm curious if it's your body that's the source of the noise. I've always been under the impression that grounding your hands to strings is to prevent this exact issue. That's why I always keep at least one hand on the bass while I'm holding it. Either that or I turn the volume off between songs.
 
#17
Sure, touching any metal part of the bass stops it, yep.

Just finished a complete copper job, minus p/g.

Better, not cured tho.
Same touch anything, including the amp or cable, ends stops it.
 
#18
Not much better, but, it looks shinier.

P5shield.jpg
 
#19
So what's next...run a ground wire from electronics to the shielding?

Shield the back of the p/g as well, run some copper over the edge of the control cavities to tie them to the p/g?


note; the 'extra wires,' black and red, in the lower right of the control cavity are from the battery compartment. Lakland put a batt box in it so one could preamp it; it's never had one.
They're loose in there, ends taped off, nothing bare.
 
#20
Chef said:
So what's next...run a ground wire from electronics to the shielding?
Click to expand...
Yes. The new shielding will have little or no effect until you ground it all. Solder wires to each section and connect them all to ground(they don't have to all go to the same point if its not convenient to do so). And yes, doing what you suggested to the pickguard is wise.
 

Latest posts

Top Bottom
Back