ground loop?? guitar wiring / di box?

[redgibson]

So I got a brand new amp (its a Bugera V22... ) I get it home and it has this horrible buzz. The buzz stops if i touch a metal part on the amp, or if i touch the 1/4" jack metal connector. So i think that means I am grounding the loop through myself, but I can't play my guitar and touch my amp at the same time :-D so... I played an acoustic through it and it didn't hum so it makes me think it is my guitar. Do i need to get my guitar rewired, or should i invest in a ground lift DI box? Has anyone used one of these / had luck with them? Any advice would be appreciated. Its a terrible intolerable persistant hum :-(

-EDIT- I should probably explain my setup. From what I've read a ground loop usually involves two power sources, in this case, its just my guitar, 1/4" jack to the amp. the only power in this case is from the wall to the amp.

 

[marnold]

Do you have another amp? Does this guitar buzz through it too?

 

[redgibson]

I do have another amp and the guitar buzzes through that. I am going to test an acoustic at lunch, and get a new best cable i can afford this evening. I think that will be a good investment even if it doesn't solve the problem, but start cheap and work my way up. It could still be a problem with the power from the wall though. So many variables!

 

[marnold]

Sounds like a good plan. If the acoustic sounds fine and the electric still buzzes through the amph even with the new cord, then we know where the problem is. Have you done any rewiring on the electric or is it stock?

 

[redgibson]

Yeah I put new pickups in the beast... but I believe it was buzzing before that... I also put a stetsbar tremelo system on it, but it uses the bridge post holes that are already in the body, so i don't think i accidentally removed the bridge grounding.

-EDIT-
From what I've read by now on les paul wiring and ground loops within the guitar, I wonder why it does NOT give me a buzz when i an playing through my effects pedal straight into my headphones?

 

[marnold]

Do you have a multimeter to check things out?

 

[redgibson]

I do have a multimeter I was poking around last night... I don't know if this is the proper way to check a ground setup but i made sure that I was able to get to every other grounded item in the guitar from every other grounded point (like checking all the vertices on a polygon) with 10k ohms. I didn't find any missing connections, so at least everything is grounded. I got a wiring diagram and I need to write out what my setup looks like to compare the two and see what's wrong. Am I checking the grounds correctly? If you have any pointers on that I'd love to try them out. Additionally- one thing i noticed is there is no ground wire coming from my bridge, but i don't know if that is the problem. if that was the problem the buzzing would stop when i touch the strings (it doesn't) but... all the same I found it to be odd.

 

[marnold]

Am I checking the grounds correctly? If you have any pointers on that I'd love to try them out.

Tung or DVM care to comment on this one? I'm no whiz with a multimeter.

Additionally- one thing i noticed is there is no ground wire coming from my bridge, but i don't know if that is the problem. if that was the problem the buzzing would stop when i touch the strings (it doesn't) but... all the same I found it to be odd.

If you have passive pickups, they must be grounded to the bridge. I'm not sure how your new trem works. With my old Tele, the ground wire was in between the bridge plate and the body. On my DK2M, the ground wire runs to the trem claw.

 

[redgibson]

so i should be able to run 10k ohms from my strings or bridge to the back of the pot where all the grounds are headed. There's definitely not a bridge wire. I've read that les pauls are to be wired to the bridge post that is set into the body. I am picking up a book over lunch that should shed some expert knowledge on les paul wiring specifics. From memory i would say i also don't have a ground to the pot from my 1/4" jack, and one of the pots does a leap-frog off another pot to the ground. that could be the ground loop right there, I'll have to take another look. At least this will certainly be a learning experience. Wouldn't it me much easier to just pick up the 2k$ jeff beck stratocaster? :happy

 

[redgibson]

New information

So now that I checked out the wiring, i've seen something that is quite strange... it appears the ground lead from the three way pickup switch goes directly to the socket on the 1/4" jack. everything else grounds to the back of a volume pot. It seems to me that I should move the ground from the switch to the back of the volume pot, and then from the pot to the socket to consolidate the 2 paths to the ground. Does this sound logical (correct?) to anyone? Thanks-

-Jeff

 

[marnold]

Assuming it's a two pickup guitar, it should be wired like this:

http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=2h_1v_1t_3w

 

[redgibson]

Alright. After rewiring the guitar, it STILL has a hum, and now i melted the top end of one of my Pots (guess i left the iron on it too long doing the soldering...) so... I got an American Fender Strat Standard :happy and it does not exhibit the same issue so there really is something wrong with the guitar. I will probably replace the electronics with an entirely new harness, but in the meantime, its nice to have a guitar that works AND a project guitar. Thanks for everyone with their help.:thankyou