Jazz Bass hum.

[Thunderpaws]

Hi everyone. 

At rehearsal this week and playing through the room’s Hartke amp. Both pickups on full and lovely full sound with no unwanted noise. 

THEN...rolled off one of the pups a tad to alter the sound a bit and my bass replied by making quite a bit of hum. Turned both full on again and him went. Turned the other pickup down a bit and hum reappeared.  

So, both pups full on = no hum

Either pup down a bit = hum

Anyone have a clue what’s up? It hasn’t done this before. It’s a MIJ Geddy. 

 

Ta. 

[dannybuoy]

Standard feature of a Jazz bass! If you've not noticed it before, it'll be the room you were in, studios and venues often have a lot more electromagnetic interference floating about then a typical home.

You can get noiseless pickups which are usually split humbuckers like a mini Precision pickup crammed into a Jazz casing, but they sacrifice a bit of top end bite. Shielding the bass including the pickup cavities could help too.

[NickA]

Conductive paint inside the pickup cavities might help a bit (connected to the ground wire if you can).  A low amp impedance will reduce the noise too, but rob you of high end.

A single single-coil pickup into a high impedance buffer in an electrically noisy room is the worst case. 

The solution is this: https://www.delano.de/jmvc_4_fe_m2/jmvc_4_fe_m2_details.html

[afterimage]

Try shielding   copper  foil 

[fretmeister]

Entirely normal.

 

1 pickup is a single coil and noisy.

both in together makes a Humbucker.

 

Nothing wrong with it. 

[KiOgon]

This is worth reading -

https://www.notreble.com/buzz/2015/04/15/solving-bass-hum-problems-grounding-vs-shielding/

[NickA]

22 hours ago, afterimage said:

Try shielding   copper  foil 

Shielding the control cavity won't help in this case as the noise is coming in from the pickups.  You can shield the pickup cavities but it still leaves the front open.  You could also shield against radiated interference by shielding the whole pickup ( surprised more pickups don't include an internal shield ).. but there is nothing much you can do about close field magnetic interference without also blocking the signal picked up from the strings ( and using thick plates of steel ).

Copper Vs spray on conductive paint?  Probably the same effect.  Commercial basses almost all use paint and it works pretty well.  Much easier to use than copper foil .. and less prone to gaps.

Humbuckers = the way to go.