Guitar earth problem HELP

Broken · Post by **Broken** » Fri Apr 01, 2005 8:07 pm

I have a Les Paul standard that puts out this buzzing sound. It goes away when I touch a piece of metal on the guitar. Obviously I am now the earth.

Where should it be earthing or should I say where should I be looking to fix this problem

Flames1950 · Post by **Flames1950** » Fri Apr 01, 2005 9:47 pm

Well, that phenomenon is normal to a degree, but I'll assume it's very obnoxious or you wouldn't be that worried about it.
I think the usual string ground in a Les Paul goes where, through the body to one of the inserts that either the bridge posts or (more likely) tailpiece posts screw into? Should come through and hook to the back of a potentiometer in the control cavity. Make sure it's got good contact.
In fact many grounding problems inside guitars come from the difficulty getting a good grounding connection on the back of those pots. It takes a lotta heat to get any solder really flowing in the connections. Check 'em all, it can't hurt.

Billy Batz · Post by **Billy Batz** » Sat Apr 02, 2005 1:27 am

Star grounding is good in guitar bodies for that purpose. I just find it easier.

Guest · Post by **Guest** » Sat Apr 02, 2005 5:09 am

Whats star grounding? Is it easy to do?

Flames1950 · Post by **Flames1950** » Sat Apr 02, 2005 7:12 am

Star grounding is (to put it simply) using the absolute minimum number of grounding points (preferably only one in the case of a guitar) to cut down on "ground loops" where there is more than one path to ground and possibly more than one voltage that ground is at.
So for your Les Paul you would want all the pickups, string ground, and tone control grounds to ground to only one potentiometer case. Any potentiometer lugs that are grounded would need to go to that same point also. Then everything is at the same grounding point and voltage potential to minimize humming and buzzing problems.

Eoin · Post by **Eoin** » Thu Apr 14, 2005 11:07 am

Flames1950 wrote:Star grounding is (to put it simply) using the absolute minimum number of grounding points (preferably only one in the case of a guitar) to cut down on "ground loops" where there is more than one path to ground and possibly more than one voltage that ground is at.
So for your Les Paul you would want all the pickups, string ground, and tone control grounds to ground to only one potentiometer case. Any potentiometer lugs that are grounded would need to go to that same point also. Then everything is at the same grounding point and voltage potential to minimize humming and buzzing problems.

What's to stop you from grounding every earth in an amp to the same point (presumably the mains earth, with the chassis grounded here too)? Obviously it would use quite a bit more wire, but is there a reason why it's not better than what you seem to get inside most amps?

Billy Batz · Post by **Billy Batz** » Thu Apr 14, 2005 11:31 am

Because you have more then 1 circuit in an amp and one can induce hum and noise into others when grounded at the same point. For those instances you want to give each circuit plenty of 'room' or paths to complete itself so it doesnt interfere with others which in a total star ground it has no choice all being at the same spot. Many people who do build amps, especially smaller simpler amps, use total star grounding but when star grounding an amp you should do what OConnor calls gallactic grounding

Thats using several local stars or nodes for each section of the amp. Maybe one for the preamp or one for each gain stage, one for the output, bias, NFB, AC etc... i.e. The input preamp node would have the jack input grounds, the cathodes, any volume control or tone control grounds then the filter cap ground. That way the circuit powered by that filter cap is able to complete itself directly. The nodes are isolated from the chassis and one by one a heavy wire connects each in turn working from the input to the power.

Thats on top of the fact that it would be difficult and messy to bring 20 grounds to one point in an amp from all over the chassis. Busses are even better for ease of building and a reliable noise method but amp chassis' are so large as long as offending grounds arent on top of each other theres plenty of paths for each voltage to take.