Hum when not touching the strings

[scuzzy]

a properly grounded bridge will stop humming when you touch strings. this topic comes up every week or so, and many jump immediately to it being a missing or inadequate bridge ground. in the majority of cases, they are wrong. it has been explained ad nauseum by electrical engineers as to why it's likely a shielding issue, but they keep regurgitating the same old song.

do what you wanna do, but a proper shielding job will likely fix your issue.

 

[scuzzy]

Solving Bass Hum Problems (Grounding vs. Shielding) – No Treble

 

[HardNHeavy]

Yep the old saying:

• If your bass hums once you touch the strings (but is otherwise quiet), you have a grounding issue.
• If your instrument hums but becomes quiet once you touch the strings, you have a shielding issue.

 

[jglunt]

If I am reading your post correctly, the hum goes away when you touch the strings?

If it is going away when you touch the strings, that doesn't sound like the usual 60 cycle hum from a single coil, that sounds like a bad ground from the bridge to the electronics. I recently had that issue after I rewired my bass kit build. I forgot to resolder the bridge wire to the rest of the ground circuit. The hum was there, but when I touched the strings, it went away (pickups are humbuckers). I realized immediately what my problem was, opened it back up, found the unsoldered bridge wire and soldered it where it belonged. Closed it all back up and the hum was gone.

Just my 2 pence.

Shielding is a good idea for sure. It will cut down on the hum. But I'm with @JC BASS 91. If the hum goes away or lessens appreciably when you put your hands on the strings, it's likely the bridge is not grounded properly. This could be the wire, or if your using coated strings like Elixirs or anything similar, it could be that the strings are not grounding to the bridge because of the coating. If you're using coated strings, take a piece of emery cloth and sand the ball end of each string to make sure there is good contact between the ball end and the bridge. That should do the trick there. Of course, if you're not using coated strings, nevermind that and just check the bridge ground.

 

[Trailertrash74]

I paid a local tech to shield my Ricky. He used some kind of shielding “paint” for the control cavity and then he used a foil on the bottom side of the pickguard.

I’ve also seen a copper colored foil used on the inside of the control cavity on a couple of my other basses.

The liquid shielding works well if applied properly. If you have drilled out wire channels from cavity to cavity, make sure the shielding is applied inside those drilled channels. Q-tips will do the job.

 

[dabbler]

Shielding needs to be grounded, which should be the ring of the jack.

If things aren't grounded, the shielding does nothing. When you touch the strings, you become the ground connection.

That the hum stops when the strings are touched means its not a shielding problem at all, as others have suggested.

Did you read my post, or the post I quoted (JC Bass said nothing about shielding, and neither did I)? My point is simply this: if the bridge (and therefore, the strings which are attached to it) is not grounded touching it changes nothing.

 

[CaperBass]

I am on the side saying bad ground. In two separate cases I had hum when not touching metal. Found a grounding wire not connected properly. Repaired and hum went away.

 

[6-3-2]

Shielding definitely helps. I have a guitar that had no shielding and once I put in shielding tape it dropped the hum by at least half. If I did it again, I'd probably use shielding paint. I'm told it stinks and it does take a bit to dry, but it seems like the much tidier option. The shielding tape is faster, but it's kind of obnoxious to install. It sticks to you, itself, it tears, etc, etc.

 

[ximun]

Shielding kit with tape and small wire for connection to ground, youtube tutos and 30 minutes of quiet time = tadaaaa

 

[Paul New]

This makes no sense to me. If the bridge and strings are not grounded, touching the strings isn't really changing there electrical situation that is causing the hum. My experience has always been that when the bridge ground is missing touching the strings does NOTHING.

Bridge Ground and Mystery Ground Issues — Haze Guitars

Solving Bass Hum Problems (Grounding vs. Shielding)

if the hum goes away when you touch the strings, then YOU are the ground.

 

[dabbler]

if the hum goes away when you touch the strings, then YOU are the ground.

If the strings are not attached to a grounded bridge, there is nothing being grounded.

 

[Paul New]

If the strings are not attached to a grounded bridge, there is nothing being grounded.

how about a situation where the pickups are connected to the bridge, but there is an open ground connection to the jack?

But the strings must be grounded too. Otherwise, why ground the bridge?

 

[micguy]

Normal 60 cycle hum of a single coil. Noise gate pedal may help.

There are two sources of hum/buzz - electromagnetic and electrostatic. Electromagnetic hum is fixed by a hum cancelling pickup - that kind of hum, if you have a single coil, and the problem is electromagnetic hum, the hum will NOT go away by touching the strings. So, the hum being talked about here is not the hum that results from a single coil.

In this case, you have electrostatic hum/buzz, which is good, because there is something you can do about it. Shielding the cavity will help, but you also need to ground the pole pieces on the pickup - while you've got it apart, and are shielding the thing with copper foil (it has to have conductive adhesive!!!), you put a strip of that foil against the pole pieces - on the back side of the pickup, and run a wire from that foil strip to the ground of the bass. If you do both those things, the bass will be quiet for electrostatic fields, but it absolutely will still hum from electromagnetic fields - that's unfixable without doing hum cancelling - just part of what you signed up for when you bought a bass with single coil pickups.

 

[micguy]

Shielding definitely helps. I have a guitar that had no shielding and once I put in shielding tape it dropped the hum by at least half. If I did it again, I'd probably use shielding paint. I'm told it stinks and it does take a bit to dry, but it seems like the much tidier option. The shielding tape is faster, but it's kind of obnoxious to install. It sticks to you, itself, it tears, etc, etc.

Shielding paint helps make the cavity a Faraday shield, but you also need to ground the pole pieces; you need copper tape for that. And I don't think the copper tape is faster - if you do a good job, it takes a while.

 

[bisticlz]

I recently went through my most frequently-used guitars and spent several evenings thoroughly shielding them, using a combination of adhesive-backed foil tape, and conductive paint. Mostly foil for simple control cavities where I could get a firm solid stick, and paint for where the router left a rough edge, and in the control cavity areas. It took some time, but cutting the foil pieces got to be zen-like after a while. Or maybe it was just the paint fumes.

Either way, guitars that used to buzz like crazy the minute my hand left the strings are now nearly silent. I can see why manufacturers skip this step, it's likely something that adds quite a bit of time and expense, but the difference is huge.

Also, everyone on Instagram should be following Amptech74 to see how *they* handle guitar electronics. It's nothing short of inspiring. https://www.instagram.com/amptech74/?hl=en

 

[bigjames]

Yes. 60 cycle noise is common with a single coil pickup.

Is your Nash shielded?

My Rickenbacker when it had single coil pickups. And it had the same type of buzzing/noise you’re describing. Especially around neon beer signs in the dive bars that I was playing.

I had my bass shielded, and it really helped. It didn’t completely eliminate the buzzing, but it reduced it.

This sounds like part of it to me. Single coils are noisy, but what you are describing sounds like the cavity may need shielding and also double checking that the bridge is grounded.

 

[mngnt]

Did you read my post, or the post I quoted (JC Bass said nothing about shielding, and neither did I)? My point is simply this: if the bridge (and therefore, the strings which are attached to it) is not grounded touching it changes nothing.

I read both quite carefully, and unless I'm misunderstanding still, I fundamentally disagree.

Touching the strings does provide a ground; the ground that's missing and thus causing the hum.

So if the bass is grounded, touching it adds nothing. If it's not grounded, touching it makes you the grounding mechanism.

That the hum goes away when the strings are touched means the problem is not shielding (or a lack thereof). It is a lack of ground that is resolved when the strings are touched. Fix that problem and the hum goes away.

 

[SulzerType2]

if the hum goes away when you touch the strings, then YOU are the ground.

No.

The excess noise you hear when not touching the strings of an unshielded instrument is interference the human body is picking up (being a wet, fatty antenna). If the bridge is grounded then this provides a path to ground for that interference, hence the 'my bass goes quiet when I tough the strings' reports that fill these forums. You yourself are not the ground in this scenario.

I fully shield all my instruments where possible (Epiphone Rivoli can't be done easily, but I use braided hookup wire to fudge it). I could remove the ground wires from the bridges of these instruments as there is no difference in background noise whether I touch the strings or not.

 

[mngnt]

No.

The excess noise you hear when not touching the strings of an unshielded instrument is interference the human body is picking up (being a wet, fatty antenna). If the bridge is grounded then this provides a path to ground for that interference, hence the 'my bass goes quiet when I tough the strings' reports that fill these forums. You yourself are not the ground in this scenario.

Have any science to back this up? A noisy bass will hum regardless of the proximity of a human. Please also explain why touching the bass elimates this supposed antenna effect.

I fully shield all my instruments where possible (Epiphone Rivoli can't be done easily, but I use braided hookup wire to fudge it). I could remove the ground wires from the bridges of these instruments as there is no difference in background noise whether I touch the strings or not.

I don't believe this is true. Try it and report back.

Edit: as I read your post again I don't even know where to start.

If your initial point is true, then all basses would exhibit this behaviour and would hum unless touched.

If your subsequent point is true, then fixing problematic ground connections would never solve hum problems.

There is undeniable evidence in this thread alone that shows that neither are true, so I have no idea what point you're trying to make.

 

[Paul New]

No.

The excess noise you hear when not touching the strings of an unshielded instrument is interference the human body is picking up (being a wet, fatty antenna). If the bridge is grounded then this provides a path to ground for that interference, hence the 'my bass goes quiet when I tough the strings' reports that fill these forums. You yourself are not the ground in this scenario.

I fully shield all my instruments where possible (Epiphone Rivoli can't be done easily, but I use braided hookup wire to fudge it). I could remove the ground wires from the bridges of these instruments as there is no difference in background noise whether I touch the strings or not.

No. Human body an antennae for emf? Lol!!