Noisy P bass when not touching metal parts help needed!

[Tjhooker]

As the bass is sheldied as far as I know I will try and check if everything in the bass is correctly connected !?

Maybe if I can get it quiet in my house then it'll be bullet proof next time I get a gig at the local power station ⚡🤘

 

[Tjhooker]

Question for those in the know.. I have five dimer switches around the house...

These things create literal noise on there own ...

Would / could this be part of the issue?

[rmorris]

So...it seems clear that your bridge/string grounding is fine. To reduce noise when you're not touching earthed metal - check the shielding. Not simply ground continuity - is the shielding complete and how it is implemented.

And yes - SCR dimmers are a major source of noise so if you can avoid them then all the better.

And don't ignore noise sources that may be in an adjoining room or building. Or, from experience, even further away.

Note on this: Coated strings can be an issue with this.

[Downunderwonder]

1 hour ago, Tjhooker said:

Question for those in the know.. I have five dimer switches around the house...

These things create literal noise on there own ...

Would / could this be part of the issue?

Sure. Turn the lights off.

[basscki]

I know this topic has gone into hibernation for a few years but it still intrigues me.

I have a well grounded P bass that hums slightly if I don't touch a metal component/strings (suggests shielding required) but the hum also disappears if the volume is fully down (makes sense) AND also when fully up (???!).

Any electromagnetic experts out there have an explanation for the max volume hum elimination behaviour?

[PaulThePlug]

^ I'd go with a new vol pot...

[hooky_lowdown]

1 hour ago, basscki said:

I know this topic has gone into hibernation for a few years but it still intrigues me.

I have a well grounded P bass that hums slightly if I don't touch a metal component/strings (suggests shielding required) but the hum also disappears if the volume is fully down (makes sense) AND also when fully up (???!).

Any electromagnetic experts out there have an explanation for the max volume hum elimination behaviour?

Is your bridge black in colour, or anything other than chrome or nickel? If so, the bridge is painted and thus not conducting. Solution is to scrap off some paint from where the ground wire touches the bridge with a craft knife or similar, so bare metal is exposed.

[basscki]

No, it's chrome and I checked the bridge wiring and contact looks good.

[hooky_lowdown]

In that case check that no part of the live wire from the pickup is touching the volume pot, it should only touch the lug. Or check the ground wire solder/connection from the pickup, see if it's connected properly, or if theres something not right with the solder joint.

[rmorris]

On 31/05/2023 at 11:13, basscki said:

I have a well grounded P bass that hums slightly if I don't touch a metal component/strings (suggests shielding required) but the hum also disappears if the volume is fully down (makes sense) AND also when fully up (???!).

Any electromagnetic experts out there have an explanation for the max volume hum elimination behaviour?

 

This is not unusual although it may be counter intuitive.

At either end of the pot' travel the source impedance "seen" by the following stage (eg amp / DI input) is at a minimum.

At mid point* of the resistance it is at the maximum.

Noise" pickup" increases with effective source impedance.

 

* assuming a log' type taper for volume pot' then this will not be the mid point of the physical travel,