Another Hum / 'Grounding Issue' Thread (Sorry!)

JimmyQ

JimmyQ

New member
Hi all,

Sorry to have to start another thread about grounding issues as I know there are plenty already, but I could use from help or advise!

I've got an LP which is suffering from an audible background hum, which stops when I touch anything metal on the guitar. So, this would appear be the famous 'wiring not grounded somewhere' issue...

I've visually checked the solder joints and wiring, and everything appears to be in order. The backs of the pots are wired together in a loop, and this loop connects to the black wire going up to the bridge (I think!). Now, I have a multimeter but I dont have a degree in Electronics! How would I go about using the multimeter to track down the cause of the problem?

I, like many other people, am somewhat unclear about how the whole grounding thing works, so any advise would be gratefully received!

Oh, and another question, is there any recommendation about what wire to use for the ground loop to the backs of the pots; size, guage, type, etc?

Many thanks and best wishes
Jim :)
 
Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

Is my LP acting up? That's really weird, cause I never noticed hum problems.

The thing I would check is the input jack, that can tend to become ungrounded. And are you sure your amp is grounded right - is this the only guitar that hums?
 
Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

bigalthethird said:
Is my LP acting up? That's really weird, cause I never noticed hum problems.

The thing I would check is the input jack, that can tend to become ungrounded. And are you sure your amp is grounded right - is this the only guitar that hums?
Click to expand...

Hey bigal,

Yeah, it is your old LP. I'm pretty sure the humming is a new thing, as I only noticed it happening the other day! One of the pots came loose a while back, so I had to open up the cavity and tighten things up, and chisel out some wood so the pickup switch sits right. Perhaps I dislodged something while I was in there...

I haven't checked the input jack yet, do you mean checking that the black wire is still attatched to the jack? I'll check it out.

As for the amp, well, plugging another guitar into this amp (Vox DA5) doesn't cause hum so I think the amp is OK. But also, when I plugged this LP into my Marshall, the hum, stopped too. So now I'm confused! How would you even go about checking the grounding on an amp?

Thanks!
Jim :)
 
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Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

I have no clue how to 'check' the grounding on an amp. But I wired up my Green guitar and it hummed a lot through my one amp. Then I tried my other guitar through the amp, and it hummed too (it never used to). I checked the plug on the amp, and the ground prong actually broke off somehow, I never noticed. So that explains the hum.

Anyways, sorry about the guitar! That sucks. I wish I could help, but I'm a huge noob when it comes to electronics.
 
Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

bigalthethird said:
Anyways, sorry about the guitar! That sucks. I wish I could help, but I'm a huge noob when it comes to electronics.
Click to expand...

Hey, don't worry about it, it's a great guitar! (and looks killer with it's new all-black finish). This is a good learning experience, the only way to get better at this stuff is by fixing stuff and making improvements to your setup.

I found this article quite helpful :

http://www.guitarnuts.com/technical/noisebucket.php

Maybe this isn't a 'not grounded' issue after all...

Still, if anyone has any thoughts as to what I may be doing wrong, please feel free to shout!

Thanks
Jim
 
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Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

JimmyQ said:
Hi all,

Sorry to have to start another thread about grounding issues as I know there are plenty already, but I could use from help or advise!

I've got an LP which is suffering from an audible background hum, which stops when I touch anything metal on the guitar. So, this would appear be the famous 'wiring not grounded somewhere' issue...

I've visually checked the solder joints and wiring, and everything appears to be in order. The backs of the pots are wired together in a loop, and this loop connects to the black wire going up to the bridge (I think!). Now, I have a multimeter but I dont have a degree in Electronics! How would I go about using the multimeter to track down the cause of the problem?

I, like many other people, am somewhat unclear about how the whole grounding thing works, so any advise would be gratefully received!

Oh, and another question, is there any recommendation about what wire to use for the ground loop to the backs of the pots; size, guage, type, etc?

Many thanks and best wishes
Jim :)
Click to expand...


i'm confused.... all electric guitars hum when you let go of the strings and metal..... and stops when you touch the metal or strings.... you the player are the ground....

I own a bunch of guitars with different pickups and some are a hell of a lot noisier then others.... Big difference in noise between even some of my Duncans of teh same model... some allow more hum then others even in the same axe....
 
Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

I'm no expert, Who, but I've definitely played guitars that make absolutely no noise no matter what.
 
Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

The ground wont "work" if you don`t touch any metal :)
 
Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

bigalthethird said:
I'm no expert, Who, but I've definitely played guitars that make absolutely no noise no matter what.
Click to expand...


depends on a lot of things like how much gain you have on the amp where the hum would be more noticable.... some guitars are much quieter then others... Maybe Active pickups are different...

But almost all guitars have the ground wired to the bridge and when you let go of the strings, and you are not touching any metal you will get some hum.... standard operation here.... I'm not too sure about active pickups like EMG's... but almost every Gibson and Fender style guitars ever made have the ground wired to the bridge... so you will get some hum when you let go of the strings and metal on the guitar. This is the way they have been designed to work...
 
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Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

I've never played active pups, but I rarely play with much gain. I completely believe you. I'm sure the quality of pup has something to do with the amuont of hum too.
 
Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

bigalthethird said:
I've never played active pups, but I rarely play with much gain. I completely believe you. I'm sure the quality of pup has something to do with the amuont of hum too.
Click to expand...

Yup all players should expect noise when they let go of their strings.... That is standard operation...

But i hate hum and noise! i have a few cheap SS amps that have so much noise i never use them... just been hanging onto them to sell when i find something i like.... I'm thinking my next amp will be a Keyboard amp oddly enough.. i can run bass and guitar PODS and other modeling multiFXs thru it as well as get a keyboard oneday soon as well.. I think it will be a good buy!

But some pickups are much noisier then others... some humbucker guitars of mine with a high gain setting are so noisey i hate them... My stock Epiphones seem to pick up lots of noise, more so then other axes i have... and when i let go of the strings the ground noise is really LOUD... Much louder then other axes i own. My Jacksons are really quiet!

I have one Duncan Custom humbucker that allows a lot of hum thru... and i have another one that is extremely quiet.. my Duncan 59's allow a lot of hum thru as well... as much as my Epiphones

A fair bit of the noise maybe my house wiring or stuff interfering...
 
Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

Thanks for the responses!

I agree that some hum is normal, particularly with higher gain. However, this hum is quite noticable. I've not noticed this issue before to this extent. There is a noticable 'pop' when I touch the strings and the hum disappears completely. It's possible that this particular amp is amplifying this hum a lot more than any of my previous amps, I guess. Or that this amp just doesn't play nice with this guitar..

My understanding it that touching the strings (or metal) does not ground the guitar. The guitar is grounded through the amp. Touching the strings actually grounds you, not the guitar! You are touching the guitar, the guitar is grounded, so the EMI (noise) that you as a person are conducting / reflecting has a route to ground through the amp.

Think about it, if you're playing upstairs, on carpet, in rubber soled shoes, you aren't going to be grounded. Quite the opposite, you're very well insulated. The guitar grounding is supplied by the ground pin of the guitar output jack, connected to the ground pin on the mains electricity supply via the amp, which runs to earth.

The amp provides the path to ground, not the player.

The link I posted above explains it quite well for me. I'm the first to admit that I don't know much about wiring and electronics! If I'm totally wrong, please somene jump in and tell me so, I have no problem with being called an ill-informed idiot!

I'm still hoping to track down why this particular guitar has started to hum through this amp, so any suggestions are gratefully recieved!

Many thanks
Jim :)
 
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Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

as i said i have a few guitars that are noisier than others..... and some amps noisier then others.. When i combine a noisier guitar and amp together it is a buzz fest!!!! My stock Epiphone LP or Exployer into my Fender Stage 100 is buzz and hum heaven! And when i let go of my strings the noise is insane!!!!

My 5150 and Peavey Classic series amps do not allow or pick up so much noise.... The difference between cheap parts and quality parts i guess...

What amp and guitar make and models are in question here?
 
Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

WhoFan said:
..
What amp and guitar make and models are in question here?
Click to expand...


It's an Epiphone LP with A2Pn / CCb combo, and a Vox DA5 mini amp. The buzzing isn't noticable when I run the guitar through my Marshall Valvestate 100 amp, so my suspicions are with the Vox...

So the guitar isn't noisy when run through a different amp, and the amp isn't noisy when plugged into a different guitar!

Maybe these two don't like eachother. :)
 
Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

JimmyQ said:
It's an Epiphone LP with A2Pn / CCb combo, and a Vox DA5 mini amp. The buzzing isn't noticable when I run the guitar through my Marshall Valvestate 100 amp, so my suspicions are with the Vox...

So the guitar isn't noisy when run through a different amp, and the amp isn't noisy when plugged into a different guitar!

Maybe these two don't like eachother. :)
Click to expand...


ya i think you are onto something.... my 10 year old high gain SS Fender Princton Chorus 2x10 practice amp can sound noisey with some guitars and yet be quiet with others... Makes my stock Epiphone humbuckers sound like i'm using single coils there is that much hum and buzz!...
 
Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

Ok, so I tracked down the 'problem', and man do I feel stupid...

The new amp has a built in Compressor effect, which was (unknown to me) switched on! :smack:

So, when the input signal became quiet, the compressor would increase the gain, amplifying the natural background hum. The hum that is present all of the time but which you don't notice unless you have the gain turned up!

What threw me was that I didnt have the gain turned up, and the noise was still quite loud. But the compressor was, of course, increasing the gain in the background!

Thanks to everyone who helped, I guess I should RTFM more thoroughly in future!

Thanks
Jim :)
 
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Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

Cool, I'm happy it's not a problem with the guitar. That would have bummed me a little bit.

By the way, can you post the link to the pictures? I accidentally erased all my PMs, and it cleared the link.

Later Jim.
 
Re: Another Hum / 'Grounding Issue' Thread (Sorry!)

JimmyQ said:
Ok, so I tracked down the 'problem', and man do I feel stupid...

The new amp has a built in Compressor effect, which was (unknown to me) switched on! :smack:

So, when the input signal became quiet, the compressor would increase the gain, amplifying the natural background hum. The hum that is present all of the time but which you don't notice unless you have the gain turned up!

What threw me was that I didnt have the gain turned up, and the noise was still quite loud. But the compressor was, of course, increasing the gain in the background!

Thanks to everyone who helped, I guess I should RTFM more thoroughly in future!

Thanks
Jim :)
Click to expand...

that would do it...
 
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