Hum goes away touching strings

[DanDBassist]

Hi Jay, I (literally) just corrected the same issue on a Vintera JB. I shielded the cavities, pickguard, and control plate. No-touch hum if not completely eliminated, reduced to a point where it is basically indiscernible.

Here is the control cavity without shielding, the two pickup cavities were the same.

View attachment 4487996

While I did not get a pic of the after (kicking myself still) here are the control plate and pickguard:

View attachment 4487997

View attachment 4487999

Be sure to get copper tape WITH CONDUCTIVE ADHESIVE. A hobby knife is nice for trimming but if you have a new, clean single-blade razor, that will work as well.

Good luck, let us know how it comes out.

Beautiful work covering everything. Conductive Adhesive is new to me. In the olden days it was recommended to use a screwdriver and press into the overlapping strips to insure that they are conductive. I love some things modern, especially electronic advances.

 

[OogieWaWa]

Sometimes us amateurs do it also...

And so much of a habit that we even do it when unplugged taking new band pictures for a newspaper article!!!

I've done shielding additions on several basses with even a slight hum. Why not? You never know when you'll have the neon sign from hell at the next gig.

 

[bassplace]

Assuming we're talking about a "normal" level of buzz:

Touching strings and having a noise reduction is actually good proof that your bridge ground is working fine. Your body is conductive. When you touch the strings, your body becomes part of the circuit - the strings are grounded (via the bridge ground), so your body is now acting like a giant meat shield, stopping noise from reaching your wiring.

The solution is shielding inside the instrument. You mentioned that you shielded the control cavity. Is that shielding grounded? If not, it's going to make the problem worse. Shielding needs to be grounded.

Check that the shielding is grounded. Check that your controls are grounded (i.e. the pots have ground wires soldered to the cases). If your pickups have plain two wire leads, consider swapping to shielded lead wires - or shield the pickup cavities and the wiring channels to the control cavity.

If you're getting really, really bad buzz, there may be another problem. Jack wired backwards, pickups with internal shielding that's on the hot side of the circuit, or even just a bad solder joint somewhere.

"Meat shield ".

 

[JeezyMcNuggles]

I have a jazz bass with stacked bridge and single pickup neck wired like a p bass with master volume and master tone. When I touch my strings the hum goes very quiet but there's noise when I take them off. Is that a bad ground to bridge issue? I've only put copper tape in my cavity and not the pickup routes

You have hum because you have a single coil pickup, not being phased by a reverse wound coil. There is nothing you can do about it. That's what a single coil does, it hums. Deal with it, or swap out your bridge for a single coil bridge pickup. Or, your neck pickup for another bucker. Although, two buckers hum a lot more than two paired singles. And there's nothing g you can do about it because they don't compliment eachother. They're just two independent pickups. A tiny bit of hum, gets doubled instead of canceled.

 

[dwizum]

A Faraday cage, which is what shielding is, needs a path to ground to work. If there is no path to ground through the jack, through the cable, through the amp, through your wiring to ground then the shielding doesn't work - until you touch the strings or the bridge to provide another path to ground using your body.

I don't mean to be pedantic, but that's essentially a misleading old wive's tale. Touching the metal doesn't cause a reduction in noise because your body provides a path to ground. If you don't believe me, you can perform a test to prove it to yourself. Get a noisy bass. Touch the strings - noise goes away. Now, while touching the strings, jump in the air - the bass will remain quiet, even when your feet aren't on the ground! If your body was making the bass quieter by providing a path to ground, the noise would come back while you were airborne.

Touching metal on the bass makes the bass more quiet because it adds your body (a conductor) to the faraday cage protecting your wiring from interference. It doesn't provide a path to ground, it makes the (already grounded) shielding significantly larger and more effective.

This may seem like nit picking, but understanding the difference is important in terms of troubleshooting the problem. Touching the strings on your bass makes the bass quieter because the (grounded) strings allow your body to have a path to ground. The bass becoming quieter is validation that the strings are well grounded. It's also validation that you need more/better shielding in the bass itself, so that your bass can be quiet all on it's own, instead of needing the additional shielding your body provides when you ground your body.

 

[MultiScaleMale]

I don't mean to be pedantic, but that's essentially a misleading old wive's tale. Touching the metal doesn't cause a reduction in noise because your body provides a path to ground. If you don't believe me, you can perform a test to prove it to yourself. Get a noisy bass. Touch the strings - noise goes away. Now, while touching the strings, jump in the air - the bass will remain quiet, even when your feet aren't on the ground! If your body was making the bass quieter by providing a path to ground, the noise would come back while you were airborne.

Touching metal on the bass makes the bass more quiet because it adds your body (a conductor) to the faraday cage protecting your wiring from interference. It doesn't provide a path to ground, it makes the (already grounded) shielding significantly larger and more effective.

This may seem like nit picking, but understanding the difference is important in terms of troubleshooting the problem. Touching the strings on your bass makes the bass quieter because the (grounded) strings allow your body to have a path to ground. The bass becoming quieter is validation that the strings are well grounded. It's also validation that you need more/better shielding in the bass itself, so that your bass can be quiet all on it's own, instead of needing the additional shielding your body provides when you ground your body.

Ok, it's not "to ground" but you're providing a path to bleed off charge from forming on the inside of the cage. Your body isn't acting as a shield.

 

[dwizum]

You're not bleeding off anything, the charge (on your body) goes to ground via the grounded instrument. The instrument is already grounded, any charge on the shielding already has a path to ground.

 

[sunbeast]

Ok, it's not "to ground" but you're providing a path to bleed off charge from forming on the inside of the cage. Your body isn't acting as a shield.

A human body is like a huge conductor and capacitor due to all of the water in it- as such we can both absorb and/or conduct noise signals and other electrical signals the same way shielding does. Without a path to ground, our bodies (just like ungrounded shielding) act as noise antennas that actually concentrate certain wavelengths of noise signals in proximity to our instruments. Without grounding or shielding our bodies can be big noise contributors/directors, but with a connection to ground (via the strings/bridge) the "meat antenna" becomes a form of shielding.

 

[HelpImaRock]

A human body is like a huge conductor and capacitor due to all of the water in it- as such we can both absorb and/or conduct noise signals and other electrical signals the same way shielding does. Without a path to ground, our bodies (just like ungrounded shielding) act as noise antennas that actually concentrate certain wavelengths of noise signals in proximity to our instruments. Without grounding or shielding our bodies can be big noise contributors/directors, but with a connection to ground (via the strings/bridge) the "meat antenna" becomes a form of shielding.

I should really consider changing my forum handle to Meat Antenna.

 

[jayroc1]

Single coil hum doesn't go away when you touch metal on the instrument. It's always there. This is a shielding issue.

So does this mean one area isn't connected with the rest of the shielding? I shielded my pickup cavities and when I touch the strings or control plate the noise reduced to practically silence.

I just uploaded an audio file. I'm tapping the string

 

[andare]

So does this mean one area isn't connected with the rest of the shielding? I shielded my pickup cavities and when I touch the strings or control plate the noise reduced to practically silence.

I just uploaded an audio file. I'm tapping the string

That sounds like no shielding. Shielding is useless if you don't connect it to ground. Solder a wire to the shielding and solder the other end to a ground point, like the back of the volume pot. Each cavity much be connected to ground. Either chain them or run individual wires to ground.

 

[Dave TB Killer]

All that shielding can be fun, or just get some split pickups.

 

[andare]

All that shielding can be fun, or just get some split pickups.

Split pickups don't hum but the rest of the electronics still do so shielding is still mandatory if you want a quiet instrument.

 

[Dave TB Killer]

Split pickups don't hum but the rest of the electronics still do so shielding is still mandatory if you want a quiet instrument.

It can be a frustration. The thing that bothers me is pedal hiss. A friend who owned a sound production company told me it was just the way the system lets you know it's alive. As long as no radio stations are coming through, all is good.

 

[andare]

It can be a frustration. The thing that bothers me is pedal hiss. A friend who owned a sound production company told me it was just the way the system lets you know it's alive. As long as no radio stations are coming through, all is good.

Pedal hiss is not a bass issue though. the more gain you add the more you raise the noise floor. Plus amps have speaker hiss.

 

[DiabolusInMusic]

So does this mean one area isn't connected with the rest of the shielding? I shielded my pickup cavities and when I touch the strings or control plate the noise reduced to practically silence.

I just uploaded an audio file. I'm tapping the string

Your shielding isn't connected somewhere if the issue is persisting. Did you remember to ground it all? Double check your ground wire coming from the bridge as well.