Help! Hum that goes away when touching strings.

[ilikeoverdrive]

Greetings forumites! I'm a long time reader of this great and expansive pool of knowlaedge which is the Seymour Duncan forum. Up to now, I've been able to solve many issues and find great ideas just by reading the posts here. But this time is a bit more difficult.

So I have two humbuckers an SD Jazz and a BKP Nailbomb, 1 volume with push pull for coil split, 1 tone and 3 way blade switch in this guitar.

I've noticed a rather loud hum coming from this guitar on all pickup selections, that GOES AWAY completely whenever I touch any metal part of the guitar (bridge, strings, etc).

It's not the amp or the cable because I tried them with my other guitars and none of them have any hum at all and yes they are all passive.

I've checked the grounding thorughly with a multimeter and everything seems to be connected (bridge to pots, strings to shielding, pots to output jack and so on). I also checked that the ground and the hot wires aren't connected in any way.

The guitar has copper shielding which has continuity throughout and is grounded to everything. Or at least that's what the multimeter tells me. Because as far as I see the only contact between the shielding and the pots which are grounded is through them touching the copper foil.

Even the screws seem to be connected to the strings and the output jack.

I'm all out of ideas and have been contemplating on just pulling all the grounding wires off and doing a star grounding or whatever. I read just about everything on the internet but it didn't seem to help much. But before I start over, I would like to try and ask this question, maybe someone sees something I didn't.

Thank you and please help!

Pics from the electronics cavity (check out that lovely Swamp Ash!):

 

[Emopunk]

Re: Help! Hum that goes away when touching strings.

I think from what you say that everything is working as expected. But wait for the wise men to confirm this..

P.S.: Lovely wood indeed, post a pic of the whole axe!

Inviato dal mio MotoG3 utilizzando Tapatalk

 

[ilikeoverdrive]

Re: Help! Hum that goes away when touching strings.

Thank you! I don't have proper lighting and everything but I'll be sure to post some pics as soon as I get that fixed

 

[ilikeoverdrive]

Re: Help! Hum that goes away when touching strings.

bump?

 

[beaubrummels]

Help! Hum that goes away when touching strings.

Welcome to the forum

If it tests correct with the back off but not when playing, then when you are putting the back on, something must be lifting the ground, or perhaps when you were testing, the face of the guitar, bridge and strings might have been touching something that properly grounded the guitar and when you closed it up and picked it up for playing took that ground away.

Test again but ensure the strings and bridge are insulated from ground physically (meaning the guitar is not laying on a metal table or something that could provide ground through the strings/bridge) and wiggle your wires while watching the meter to make sure there isn't a solder joint that loses its connection when the back is on and putting any pressure on the wires.

 

[ilikeoverdrive]

Re: Help! Hum that goes away when touching strings.

Welcome to the forum

If it tests correct with the back off but not when playing, then when you are putting the back on, something must be lifting the ground, or perhaps when you were testing, the face of the guitar, bridge and strings might have been touching something that properly grounded the guitar and when you closed it up and picked it up for playing took that ground away.

Test again but ensure the strings and bridge are insulated from ground physically (meaning the guitar is not laying on a metal table or something that could provide ground through the strings/bridge) and wiggle your wires while watching the meter to make sure there isn't a solder joint that loses its connection when the back is on and putting any pressure on the wires.

Thank you, sir, for your reply!

If by back you mean the back plate (cover) for the electronics cavity, then I'm afraid it doesn't make any difference whether it's on and screwed in place or off.

I'm afraid the back plate has nothing to do with the hum I'm experiencing.

Again, the hum is very prominent especially when playing with a loud clean tone and it goes completely away the moment I touch the bridge, the strings or any metal part on the guitar. Even touching the pickup posts silences the hum!

But, for example, if I'm just holding the guitar without touching any metal on it, the hum is quite loud. And it gets A LOT LOUDER if I, for example hover my hand or touch the sides of the pickups (uncovered pickups, that is). And if I face the guitar to, say, a power supply or the electrical socket, the hum becomes unbearable! But even then, if I touch any metal on the guitar, it will again go completely quiet.

I checked for continuity 20 times today alone, I thing I'm becoming compulsive about it, lol. And the multimeter tells me that everything (both ground and hot) are wired accordingly.

Let me know if you have any suggestions!

 

[AlexR]

Re: Help! Hum that goes away when touching strings.

It is normal for you grounding the strings/metal parts and the hum to vanish - thats how it works. It does sound like you have a lot of interference about, and your pickup wires are quite long out of the shielded outer.

You might want to shorten some of you wires so they don't cross over as much. And maybe replace the output wire with a shielded one too.

I'm wondering if the cavity shield isn't somehow doing the opposite.

 

[Hyperborea]

Re: Help! Hum that goes away when touching strings.

Well, when you touch the strings you are being grounded and your noise is going away. So, the string ground seems to be ok. If the noise is when you bring your hand near the pickups then there is something wrong with their wiring. Is it both of them?

As I look more closely, I don't see that the cable shielding from the pickups is grounded. That's the bit of silvery blue foil that's sticking out of the pickup cable. That cable shielding is connected to the shielding ground of the pickup and without that grounded in the control cavity that could be the source of your noise.

 

[ilikeoverdrive]

Re: Help! Hum that goes away when touching strings.

Well, when you touch the strings you are being grounded and your noise is going away. So, the string ground seems to be ok. If the noise is when you bring your hand near the pickups then there is something wrong with their wiring. Is it both of them?

Thanks for the feedback.

Yes, both of them hum pretty badly, although the worst offender seems to be the BKP. Probably because it has more output? I don't know..

As I look more closely, I don't see that the cable shielding from the pickups is grounded. That's the bit of silvery blue foil that's sticking out of the pickup cable. That cable shielding is connected to the shielding ground of the pickup and without that grounded in the control cavity that could be the source of your noise.

Huh, good observation. What is that silvery thing anyway? Is it even a wire? I'm not sure but I think it's just insulation. I checked the diagrams for both pickups (SD and BKP) and thought that the green and silvery wires (Seymour Duncan 4con) and black and silvery wires (BKP 4con) were ground... right? Right?

I need a second opinion on this, but if they're wrong then at least I won't have to resolder everything..

 

[ilikeoverdrive]

Re: Help! Hum that goes away when touching strings.

It is normal for you grounding the strings/metal parts and the hum to vanish - thats how it works. It does sound like you have a lot of interference about, and your pickup wires are quite long out of the shielded outer.

You might want to shorten some of you wires so they don't cross over as much. And maybe replace the output wire with a shielded one too.

I'm wondering if the cavity shield isn't somehow doing the opposite.

The hum is anything but normal. Seymour Duncan and BKP are both respectable companies and, if a Chinese Ibanez with mystery El-cheapo passive pickups is DEAD QUIET at the same settings and plays just as loud, then there is a problem.

The wires are kind of long, but I'm not sure it's out of the ordinary.

And would replacing only the output wire with a shielded one make the difference?

As for the cavity shield, your guess is as good as mine at this point. The multimeter says it's grounded and I don't know what to say anymore.

 

[ilikeoverdrive]

Re: Help! Hum that goes away when touching strings.

I rechecked and I'm pretty sure that the green and bare wires for the SD and the black and bare for the BKP are the ground wires.

Is it possible that not having them, the tone pot ground and the shield ground soldered in the same place as the bridge ground (on top of the volume pot) affect the amount of noise?

If it was a conductivity issue at least I'd know what I would be fixing. But I don't have the slightest idea. And the fact that my cheap Chinese Ibanez is perfectly quiet just drives me nuts

 

[Lysergene]

Re: Help! Hum that goes away when touching strings.

The outer braided shield wire needs to be connected to ground, either the back of the volume pot or the ground terminal of the switch. Can't really tell if you have done this from the photo.

I'm no wiring expert, wait for a next opinion!

 

[AlexR]

Re: Help! Hum that goes away when touching strings.

You are getting noise. Humbuckers don't hum by their design, so something in your wiring is making them pick it up. Any shielded cable will assist, and the 2 wires to the jack is a longer than average run (like the pickup wire which you should have already noticed has shielding too).

I would remove the bare pickup wires to a back of pot situation. They should never be added to pickup wires unless that connection is ground at all times. And I would use the back of pot for your grounding too for the circuit if it isn't so already. Use a cloth covered wire for the pot ground connection and it will have some protection.

 

[BloodRose]

Re: Help! Hum that goes away when touching strings.

I have a couple of guits that do this as well. I get hum til I touch the strings, then dead quiet. Had a well respected tech check it and he said this is normal..?? So, Im curious how this thread plays out...

 

[ilikeoverdrive]

Re: Help! Hum that goes away when touching strings.

The outer braided shield wire needs to be connected to ground, either the back of the volume pot or the ground terminal of the switch. Can't really tell if you have done this from the photo.

I'm no wiring expert, wait for a next opinion!

I'm not sure about that. I mean, one of the ground wires from both pickups is bare so it should make contact with the shielding as well. Grounding that should be enough to ground the cable shield as well, right?

 

[ilikeoverdrive]

Re: Help! Hum that goes away when touching strings.

You are getting noise. Humbuckers don't hum by their design, so something in your wiring is making them pick it up. Any shielded cable will assist, and the 2 wires to the jack is a longer than average run (like the pickup wire which you should have already noticed has shielding too).

So I should start by replacing the ground running to the outputjack? or both ground and hot? or should I go the extra mile and just rewire everithing the way it is but with shielded wire? Or star grounding and shielded wire???? Good God, I don't know but I'll wait a bit more for opinions and do it next week.

I would remove the bare pickup wires to a back of pot situation. They should never be added to pickup wires unless that connection is ground at all times. And I would use the back of pot for your grounding too for the circuit if it isn't so already. Use a cloth covered wire for the pot ground connection and it will have some protection.

Wait, I'm confused. Do you mean the tone pot (round) and the bare wire running between it and the volume pot (square shaped pot)? Because that's not a pickup wire. That's just a bare wire grounding the tone pot to the vol pot (and thus to everithing else). And that's another strange thing because, although I don't have any wires running specifically from the shielding to any of the pots, everything reads connected when tested with a multimeter (shield to pots, shield to bridge and so on). Wouldn't just the shielding be enough to connect and thus ground the pots even between each other? I mean the switch isn't grounded with a separate wire but it's still tests grounded...

Or do you mean the bare wires which are one of the two ground wires in a 4con pickup? Because as far as I know, they need to be connected to ground. Not removed. Didn't the manufacturer put them in there in the first place? How are you supposed to remove them?

Please explain if you have the time. You might be on to something but I didn't quite get it. Thanks

 

[ilikeoverdrive]

Re: Help! Hum that goes away when touching strings.

I have a couple of guits that do this as well. I get hum til I touch the strings, then dead quiet. Had a well respected tech check it and he said this is normal..?? So, Im curious how this thread plays out...

No Sir, this kind of hum that goes away when touching the metal is NOT NORMAL. That's what a lazy or just plain confused tech will say to save face. I had a tech tell me that too, that's when I decided I need to do this myself...

I have three other guitars, one of which is a cheap Chinese Ibanez SA120 and it's as quiet as a gagged church mouse in a vacuum cleaner and plays just as loud. With passive pickups no less!!

I'll post the solution loud and clear for everyone as soon as I have it...

 

[orpheo]

Re: Help! Hum that goes away when touching strings.

No you are wrong. Your guitar is supposed to go quiet when you touch met parts. You are grounding yourself. I have build over 100 guitars, serviced hundreds more. They all have this to some degree.

As to why it goes away: you are the cause of the noise as you are, simply put, an antenna. The pickups pick that up.

The blue-silver foil is just the lining of the cable. The bare metal wire is what you should connect to ground.

 

[ilikeoverdrive]

Re: Help! Hum that goes away when touching strings.

No you are wrong. Your guitar is supposed to go quiet when you touch met parts. You are grounding yourself. I have build over 100 guitars, serviced hundreds more. They all have this to some degree.

As to why it goes away: you are the cause of the noise as you are, simply put, an antenna. The pickups pick that up.

The blue-silver foil is just the lining of the cable. The bare metal wire is what you should connect to ground.

With all due respect, I know a guitar should be quiet. I didn't say think, or believe, I said know because I have other guitars that are quiet given the EXACT same conditions. Now I don't know about your personal experience, maybe your place is highly susceptible to interference and such and thus your guitars are, probably, noisy even when properly grounded. But I still doubt that.

I know the human body can act as an antenna but a properly grounded/shielded guitar should pick up next to no noise. They are humbuckers. Note: HUM-buckers.... Guess it'd be better if I just recorded the noise, but honestly the people who have heard this know what this is without any further explanation.

All I know is that I want this guitar to match my quiet cheap Ibanez with passives. Not to mention all the other guitars I played.

 

[orpheo]

Re: Help! Hum that goes away when touching strings.

Fine. If you don't want to read up in the science suit yourself.

Again, I've (likely) worked on more guitars than you. I'm too tired to try and explain.

Your body acts like an antenna. Not 'can act'. It does. Other guitars can be dead quiet with excessive shielding. Cheap guitars are often heavily shielded with shielding paint etc.

A humbuckers bucks the hum perfectly cause if they didn't you'd still have hum even when you touch the strings.

You are the cause of the hum, not the guitar. learn the science.