• 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.

Hum / Buzz Problem

P

papmech

Jul 19, 2008
19
0
#1
Hi all.

I just finished my first project bass, and I am glad as hell it's over. I don't take inhaling solder fumes too well.

After putting everything together, I was certain that the pickups wouldn't produce any sound on my first try, but they did, EXCEPT that these pair of humbucking Dimarzio pickups (Area J) are humming and buzzing like there's no tomorrow!

The situation is like this. When I don't touch the bass, and I turn up the volume a fair bit, I start to hear the hum. However, when I touch the grounded bridge or the strings or any of the pots, the hum almost disappears.

My bass is wired as such:

Neck / Bridge Pickup (4 wires) ----> DPDT (one for each pickup, switch between Parallel and Series) ----> Volume Pot (one for each pickup) ----> DPDT (switch between Neck + Bridge in Parallel or Series) ----> Tone ----> Output

Total of 3 DPDT switches, 2 volume pots, 1 tone pot, 1 orange drop cap.


I checked all my connections, and nothing seems to be out of the ordinary. However, I am inclined to believe that I messed some part of the circuit up, than that the pickups are producing the hum (they are humbucking after all!).

What are the possible causes for this hum?
 
#3
If touching the strings fixes it, it could be a grounding issue as well as hum. You can test for continuity between all of the grounded areas with a multi.

99% of basses I have ever played exhibited this "problem" to varying degrees. Most you can't really hear it most of the time but it's there at a low level, occasionally one will have it very loudly like you are experiencing. Gain staging will have a big effect on the audibility of the hum/buzz.
 
#4
Floyd Eye said:
It's 60 cycle hum that is inherent with SC pups. Sounds to me like the humbuckers you put in there are not wired correctly.
Click to expand...

They seem to be wired correctly. I can switch between parallel and series (one mode is brighter and softer than the other) for both pickups no problem. Is there any other way I can test for this?

cassius987 said:
If touching the strings fixes it, it could be a grounding issue as well as hum. You can test for continuity between all of the grounded areas with a multi.
Click to expand...

There's continuity between the ground portion of the cable jack on the strings, so I don't think it's a continuity issue.
 
#6
Is it a low hum, or a high pitched buzz? If it goes away when you touch the strings, it's sounds like a ground/buzz problem.

Also, when you wire two pickups in series, you have to be careful with grounds. When in series, the first pickup has one end grounded. What would normally be hot then goes to what would be ground on the other pickup.

You can't have the volume control wired up for the first pickup when sending it to the second in series. You need to bypass it when they are switched into series.

Also make sure all the bare wire grounds from the pickups stay on ground, and not into the other pickup in series.

Lastly make sure you have all the pots grounded as well as any shields (foil, paint. etc.) you might have.

I used to wire all my basses up like this.

Can you post the wiring diagram you used?
 
#7
I had a similar problem on my first p bass... Shielding fixed it for me. My first thought was ground and I rechecked it several times but all looked well. I did several searches on hear and found out that it was shielding.
 

Latest posts

Top Bottom
Back