Shielding a guitar - hum persists

[Pillimees]

Evening, gents.

 

I've got here a nice '89 Gordon Smith GS1.5 that I've just lovingly shielded, but the sneaky guit-fiddle still insists on humming. It's the sort of hum that disappears when you touch the strings or any other grounded metal part, so it would seem my shielding job was inadequate. Thus, a question to those with experience in this - would any of the following reintroduce so much noise as to completely foil a shielding attempt?

 

1) the pickups aren't shielded (even the humbucker's cover is plastic). They also sit fairly high out of the body as the guitar is a flattop. I'm hesitant to shield the pickups themselves, as the guitar's kind of old and actually belongs to a friend, so any damage to the pickup windings would be Very Bad

[ocnor]

If the hum stops when you touch the strings then you most likely have a problem with the bridge ground wire .

[isaac42]

My thought exactly. Hum is much more often a grounding issue than a shielding issue. I have solved similar sounding problems several times by cleaning or replacing the output jack, and at least once by cleaning the bridge grounding lead.

[weg]

 

If the hum stops when you touch the strings then you most likely have a problem with the bridge ground wire .

 

 

x2

 

Also stwemac sells some copper paint that I like better than the tape for shielding. Easier to fit into different places than the tape.

[Pillimees]

Le sigh...

 

The bridge ground wire is fine. If it weren't, touching the strings would have no effect on hum (except for perhaps making it even louder). And yes, I checked it with an ohmmeter.

 

 

Also stwemac sells some copper paint that I like better than the tape for shielding. Easier to fit into different places than the tape.

 

That's nice. I prefer tape, as it can be soldered to, and is less permanent than paint.

[ocnor]

 

Le sigh... The bridge ground wire is fine. If it weren't, touching the strings would have no effect on hum (except for perhaps making it even louder). And yes, I checked it with an ohmmeter.

 

 

When you touch the strings your body acts as a ground and the hum/buzz stops. If this is what's happening then your guitar is not grounded properly. If the hum became louder when you touched it then it would mean something is wired backwards. Use your ears not your ohm meter.

[Pillimees]

And how, pray tell, are you grounding the guitar? Are you standing barefoot on a metal plate? Or touching a water pipe, perhaps?

 

Your body acts as a shield, and the guitar is grounding you.

 

Your body, on account of being much larger than the wiring inside the guitar, picks up noise much better. When you're simply holding the guitar without touching any grounded metal parts, you simply radiate any noise you pick up right into the guitar's wiring. Hence the noise. As soon as you touch a grounded metal part on the guitar (such as the strings), you're grounded through said metal part, and the noise will disappear, as it's being shorted to ground. This is why shielding the guitar should help, as it'll provide a permanent, always-grounded layer of protection between the noise and the guitar's circuitry.

 

Here's a couple of fun experiments to try. Plug your guitar into your amp and turn it up. Don't touch any metal parts. Unless your guitar is well shielded, you should hear some noise. Now place your hand over any of the pickups, while still avoiding the strings. The noise should increase. Try moving your hand closer to, say, a computer monitor. The noise should increase even more. Now put the guitar away from your body (while it's still plugged in). The noise should decrease. This shows how your body is acting as a channel for noise. And unless there's another shield in place between you and the guitar, you'll have to ground yourself through the guitar to avoid bleeding that noise into the circuitry.

 

Also, when you touch the strings and the hum increases, it's a sign that the bridge (and hence the strings) isn't grounded. The reason is that you're inserting the noise into the strings, which in turn concentrate it right above the pickups (which are extremely effective antennae), rather than sending it to ground via the bridge.

 

Now, does anyone have any helpful suggestions?

[FuzzShifter]

I have a great suggestion....

 

Touch the strings, while holding your guitar.

 

I know it sounds simple, but it works.

 

As for the shielding... if you have less interference, static, and random noise, your shielding is proper.

 

 

BTW, buy a noise gate. It works when not touching the strings.:poke:

[Pillimees]

 

I have a great suggestion.... Touch the strings, while holding your guitar.

 

I said, helpful suggestions. If that sufficed, I wouldn't have bothered with the shielding in the first place.

 

 

As for the shielding... if you have less interference, static, and random noise, your shielding is proper.

 

As I explained in the first post, the guitar still gets hum, therefore the shielding wasn't proper. Hence this whole thread.

 

Honestly, is it so hard to understand what I'm asking for?

 

 

BTW, buy a noise gate. It works when not touching the strings.:poke:

 

Yeah, and having it clamp down on long sustained notes is ever so nice.

No, thanks. I want to kill the hum at the source, before it gets into the signal chain.

[weg]

Seriously dude quit being a dick.

 

Star ground, shield everything you can and don't play near florescent lights or computer monitors. If it's really that big of a deal you could redo the wiring from the neck pickup with a shielded one...

 

You said yourself you didn't completely shield everything, so thats where I would personally start.

[Pillimees]

 

Seriously dude quit being a dick.

 

Right, I'm sorry for getting upset at the fact that all the suggestions presented in this thread so far, while well-intended I'm sure, have been irrelevant at best and grossly misinformed at worst. Sorry for trying to re-elaborate my problem in what I thought was a fairly calm and polite manner. Sorry for actually taking the time to educate the would-be helpers and pointing out their mistakes. Sor-ry.

 

 

Star ground, shield everything you can and don't play near florescent lights or computer monitors. If it's really that big of a deal you could redo the wiring from the neck pickup with a shielded one...

 

As I explained in the first post (I feel like I've said that already), it's not my guitar, and it's kind of old, so I don't want to touch the pickups if at all possible. Also, the owner of the guitar will inevitably be playing near sources of noise, so that suggestion of yours has little merit.

 

Re star grounding, how exactly is that going to help me?

 

 

You said yourself you didn't completely shield everything, so thats where I would personally start.

 

The first actually useful suggestion in this thread so far. Thank you, sir, you have given me hope again (and that wasn't sarcasm).

 

Now, is it your experience that the guitar's electronics have to be completely enclosed? Would even the smallest hole in the shielding reintroduce all the noise? If so, how would you suggest I shield the channels that the pickup wires run through?

[ocnor]

 

Right, I'm sorry for getting upset at the fact that all the suggestions presented in this thread so far, while well-intended I'm sure, have been irrelevant at best and grossly misinformed at worst. Sorry for trying to re-elaborate my problem in what I thought was a fairly calm and polite manner. Sorry for actually taking the time to educate the would-be helpers and pointing out their mistakes. Sor-ry.

 

 

There you go being a dick again. Who are you to "educate" people when it's obvious that you don't know what you are doing. I've been rewiring guitars for 30 years and some people here have even more experience. Everyone has told you that it is a ground problem or something is wired backward. A guitar with humbuckers will not have the problem that you described even if it has poor shielding. You just won't own up to the fact that you made a mistake. I doubt that you will receive any more help because of your bad attitude and the fact that you like talking down to people. I guess you will have to go and tell your friend that you were too stupid to fix his guitar. I think I'll go and play one of my NON-Humming/Buzzing guitars.

[Pillimees]

 

There you go being a dick again. Who are you to "educate" people when it's obvious that you don't know what you are doing. I've been rewiring guitars for 30 years and some people here have even more experience.

 

Perhaps you can name some of those people with even more experience, so I can contact them directly and skip the ugliness that this thread is being turned into.

 

I've successfully shielded several guitars, and while I cannot claim 30 years of experience (I'm not even that old), I do have a clue about what I'm doing. This is the first time I've run into problems like this, and I was really hoping I'd get an answer from here. Instead, I get bombarded with ill-informed replies that seem to be based on common internet myths. I cannot possibly begin to fathom how someone with 30 years of experience can claim that the guitarist is grounding the guitar.

 

 

Everyone has told you that it is a ground problem or something is wired backward.

 

Can you stop the condescending for a moment and actually explain how this can be a grounding problem? You can start by refuting the explanation I gave in post #7.

 

 

A guitar with humbuckers will not have the problem that you described even if it has poor shielding.

 

Firstly, the neck pickup is a single coil, as I've mentioned already.

 

Secondly, there's more to a guitar than just the pickups. Wires, pots and other components also pick up noise if not properly shielded.

 

 

I doubt that you will receive any more help because of your bad attitude and the fact that you like talking down to people.

 

I've barely received any help at all.

[isaac42]

 

And how, pray tell, are you grounding the guitar? Are you standing barefoot on a metal plate? Or touching a water pipe, perhaps? Your body acts as a shield, and the guitar is grounding you . Your body, on account of being much larger than the wiring inside the guitar, picks up noise much better. When you're simply holding the guitar without touching any grounded metal parts, you simply radiate any noise you pick up right into the guitar's wiring. Hence the noise. As soon as you touch a grounded metal part on the guitar (such as the strings), you're grounded through said metal part, and the noise will disappear, as it's being shorted to ground. This is why shielding the guitar should help, as it'll provide a permanent, always-grounded layer of protection between the noise and the guitar's circuitry. Here's a couple of fun experiments to try. Plug your guitar into your amp and turn it up. Don't touch any metal parts. Unless your guitar is well shielded, you should hear some noise. Now place your hand over any of the pickups, while still avoiding the strings. The noise should increase. Try moving your hand closer to, say, a computer monitor. The noise should increase even more. Now put the guitar away from your body (while it's still plugged in). The noise should decrease. This shows how your body is acting as a channel for noise. And unless there's another shield in place between you and the guitar, you'll have to ground yourself through the guitar to avoid bleeding that noise into the circuitry. Also, when you touch the strings and the hum increases, it's a sign that the bridge (and hence the strings) isn't grounded. The reason is that you're inserting the noise into the strings, which in turn concentrate it right above the pickups (which are extremely effective antennae), rather than sending it to ground via the bridge. Now, does anyone have any helpful suggestions?

 

 

How can we possibly help, when you apparently already know so much more than we?

[isaac42]

 

I've barely received any help at all.

 

 

Actually, you have. You just don't recognize it as such.

[Pillimees]

 

Actually, you have. You just don't recognize it as such.

 

What help I've received, I've recognised and responded to. weg's last post contained a genuinely useful, if a little lacking in detail, suggestion, which I fully intend to follow as soon as he elaborates a bit more.

 

Meanwhile, the rest of you keep going on about this being a grounding issue, even after I've confirmed and demonstrated that the grounding on the guitar is fine. How exactly is that helpful?

 

If you really want to help, explain please how it can be a grounding issue. As in, really explain, not just claim it to be so, because, as per ocnor, I'm stupid and don't know what I'm doing.

[hjcooper]

 

...how would you suggest I shield the channels that the pickup wires run through?

 

 

copper tubing found in any hardware or plumbing store

[Pillimees]

Good idea, thanks! I'll look into this. Hopefully I can find a store that carries something like that, and hopefully it's flexible enough.

[FuzzShifter]

http://en.wikipedia.org/wiki/Faraday_cage

 

Don't be an asshole. Answers have been given to your questions.

 

It just may be possible that you are too dense to understand.

 

Electric guitar produce noise. Try a low-impedance active system to combat this.

 

I don't understand the problem with touching the strings....

 

If touching the guitar isn't an option, try unplugging it.

[Pillimees]

http://en.wikipedia.org/wiki/Faraday_cage

I'm confused. The link is relevant, yes, but I understand the principle behind a Faraday cage and electromagnetic shielding already. So what exactly was that supposed to be in aid of?

 

Don't be an asshole. Answers have been given to your questions.

Yes, they have. Unfortunately, the answers have also been drowned in a sea of misguided advice, petty bickering and name-calling.

 

It just may be possible that you are too dense to understand.

There we go with the name-calling again. Don't you have someone else to pick on?

 

Electric guitar produce noise.

No kidding?

I know electric guitars produce noise. I also know from experience that it's possible to greatly reduce this noise. That's what I'm trying to achieve with this guitar, and that's what I'm having problems with.

 

Try a low-impedance active system to combat this.

Sorry, not an option.

 

I don't understand the problem with touching the strings.... If touching the guitar isn't an option, try unplugging it.

If you don't understand the problem, then why are you posting?

 

My goal is for there to be as little noise as possible, and for there to be no difference in noise when touching the strings vs. not touching them. Do you understand now?

[newmaxnew]

Does this guitar have humbuckers?

 

I had a similar problem with my last wiring job. When I touched the strings the hum went away. You know what the problem was? A band ground on one of the pots. Humbucker guitars should not have hum issues at all if all of the grounds are in place and you didn't wire up any ground loops. The reason for star grounding is to avoid ground loops that cause hum.

 

If every one of your grounds is connected, then you probably created a ground loop, Try grounding everything to one point (that is star grounding).

 

Max

[Pillimees]

It's got a single coil in the neck and a humbucker in the bridge.

 

Thanks for the suggestion. I think I'll just redo the whole wiring in the control cavity when I get the time.

[Pillimees]

Thanks for the good luck wishes.

 

Have you tried playing the guitar somewhere else? As in, not in your house? Because it does sound like you simply have a lot of noise in the air that's coming from outside your house.

 

I'm not giving up hope yet. While troubleshooting the GS, I finished shielding a guitar for another friend (an Aria Pro II Fullerton), and that was as quiet as a mouse when I was done. So I'm going to go and give a couple of the suggestions I've received in this thread a shot over the weekend.

 

As for the GS, the owner is pretty attached to her, and even if he did decide to sell it, I'd try and grab it for myself

 

Thanks again, I appreciate you taking the time to share your experiences.

[phy7ajw]

Good thread.

 

Pillimees, you've clearly read around the subject and understand the concept of shielding and you're right, most people on this thread probably don't understand that the strings end up grounding the player. They've also probably stopped reading the thread by now but that's their problem...

 

I'd point anyone who's still reading at this page on Guitarnuts for another good explanation. An excellent site.

 

The noise issue may well be outside of the guitar, as infinitemonkey suggests. I've shielded all mine and I consistently have a noise problem when I play at a friends house, even with a fully copper-shielded Strat with SCN noiseless pickups (which is basically a set of three stacked humbuckers). At his place I play into my PodXT and then into a mixer via balanced cables and I suspect it's an electrical noise issue getting in there somewhere but haven't experimented yet because I just tolerate it.

 

Can you plug into a variety of kit and notice any difference in noise? I'm thinking:

 

Using a battery-powered rig would be most interesting (and that's reminded me to put my Pandora into my gig bag for the next jamming session/noise experiment!). Any good?

[Pillimees]

Alas, I don't have another amp, nor any multi effects devices. The only other piece of gear that I can plug into is my Mackie Onyx Satellite with its instrument inputs. When I plug into that, the guitar is quiet, as are all others, even if sitting right in front of the computer, and even though there are several power transformers nearby. So it would seem that the amp is at fault here, if it weren't for several other guitars that get along with it just fine.

 

As for cables, I use good quality Proel ones, same ones that I also use on stage and in the studio. Any others I might be able to dig up from years past would only be worse.

 

Anywho, I had time to tinker with the guitar over the weekend, and found at least one problem - the contact between the foil on the back of the pickguard and the neck pickup cavity shield wasn't good enough. Pressing down on the pickguard reduced the noise somewhat, so I added extra pieces of copper tape to improve the contact, which helped considerably. I also re-did the wiring and isolated any places where pot shells might touch the copper or the foil on the back of the control cavity cover and possibly create ground loops. Overall, hum is tolerable now, though not entirely disappeared. I'm going to have the owner check it with his rig, and if it's OK we'll leave it like that.

 

phy7ajw, thanks for your suggestions, your input is much appreciated.