Annoying Guitar Hum

**Cincy2** · 03-12-2019, 06:33 AM

I just had the pickups on my Gibson L5 replaced. Last night I noticed an annoying low level hum coming from the amp. If I touch the tail piece, the hum goes away. Grounding issue? The amp has a good ground with a 3 prong plug as does my outlet. I don't have this problem with my other amplified guitars. I'm guessing that the pickup ground line was not correctly connected to the guitar's output jack. Anyone with an electrical background have any ideas?

Thx
Eric

**Jabberwocky** · 03-12-2019, 06:58 AM

It is grounding issue, Eric.

**Brian B** · 03-12-2019, 07:08 AM

Originally Posted by Jabberwocky

It is grounding issue, Eric.

^^^ This. ^^^

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**Tal_175** · 03-12-2019, 07:29 AM

If the hum goes away when you touch strings, tailpiece etc. than it not a grounding issue. That's means grounding is working. It's normal.

**Jabberwocky** · 03-12-2019, 07:29 AM

Or maybe it just didn't know the words to Stairway to Heaven.

**ragman1** · 03-12-2019, 10:18 AM

Annoying Hum

Personally, I think it's the traffic on the M9.

**rio** · 03-12-2019, 11:05 AM

Yeah any hum that disappears when you touch metal is a ground issue.

Out of curiosity, if any of you know, what would a hum that doesn’t disappear when you touch metal mean? I’ve never even really noticed it much at all but when I started recording last month the guy doing the recording pointed it out. Happens through all amps. Live playing it isn’t noticeable at all, probably why it didn’t bother me, but after he pointed it out I see why he doesn’t want it on the recording. On a ‘70 L5 could it be something age related? I don’t want to get into rewiring it if that might not even fix it, particularly since I can live with it. The hum is around a low B if that makes any difference.

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**Tal_175** · 03-12-2019, 11:09 AM

Originally Posted by rio

Yeah any hum that disappears when you touch metal is a ground issue.

Out of curiosity, if any of you know, what would a hum that doesn’t disappear when you touch metal mean? I’ve never even really noticed it much at all but when I started recording last month the guy doing the recording pointed it out. Happens through all amps. Live playing it isn’t noticeable at all, probably why it didn’t bother me, but after he pointed it out I see why he doesn’t want it on the recording. On a ‘70 L5 could it be something age related? I don’t want to get into rewiring it if that might not even fix it, particularly since I can live with it. The hum is around a low B if that makes any difference.

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I believe it is the opposite. Hum that disappears when you touch metal means no ground issue. If it doesn't disappear than it IS a grounding issue.
Pickups have ground connection usually the metal cover or metal shield of the wire. Pots have ground too. You extend a wire connected the these and make sure it's in contact with the metal hardware. That usually through the tailpiece in archtops. That's why when you touch metal parts hum stops. If they don't then there is a grounding issue. That means that ground wire is not connected to the hardware.

**grahambop** · 03-12-2019, 11:22 AM

Here's a comprehensive article on the subject:

Minimising Noise In Electric Guitar Rigs |

**BBGuitar** · 03-12-2019, 11:35 AM

Run a wire (clip lead) from the tail piece to the nut on the output jack.

1. Hum goes away the ground to the tailpiece not complete.

2. Hum does not go away it is something else.

**rpjazzguitar** · 03-12-2019, 02:52 PM

Each pickup individually?

Both together?

All controls work the way they should?

Happens with a different amp and cable? And, one amp, one cable straight in, no chance for ground loops?.

Make any difference if you change rooms or turn the guitar this way or that?

I've had this happen, but I can't remember what it turned out to be. I don't recall having to rewire anything to solve the problem.

I guess, somehow, electrical ground is floating, voltage-wise. So, when you touch the strings (which are connected to the outside of the jack and the bodies of the pots and so forth), you bleed off the unwanted voltage (you become part of the ground).

So far, I haven't figured out what you could do to create this hum, assuming that you wanted it. Maybe the body of a pot not connected to ground?

**Danny W.** · 03-12-2019, 04:33 PM

There's a ground wire that runs from the harness ground to the tailpiece.

It's disconnected at one end or the other. After having the pickups replaced, it might be missing altogether

Take an ohmmeter and measure from the output jack mounting nut to the tailpiece--should be around 0 ohms.

Danny W.

**sgosnell** · 03-12-2019, 05:37 PM

I have an electric mando I built myself. The tailpiece is entirely wooden, and I made it myself from wood. There is no metal anywhere in or on the tailpiece, and there has never been a ground wire run anywhere to it, so the strings are not grounded, nor have they ever been. I keep meaning to apply some copper foil tape and ground the strings, but I just haven't gotten around to it, even after all these years. It has a rather loud hum unless I touch the strings. When I touch the strings, the hum goes away. I'm not trying to explain the physics, just sayin'....