Why do some Jazz Bass pickups make noise if a pole piece is touched, others don't?

[DirkP]

I have 4 Jazz Basses, all have traditional Fender Pickups: a `78 Jazz, a US Vintage Series '64 Jazz, a Noel Redding MIJ '65 Jazz and a MIJ '70s Jazz with CS '60s pickups.
I assume that all of the instruments are grounded properly.

The '78 and the Noel Redding make a loud unwanted noise if I accidently touch the pole piece under the E-string with my thumb, the others don't. I remember when I first tried a Fender Jazz long long ago (a '62 Vintage Series) it made that unwanted noise, too. The shop-manager looked a bit puzzled, but I simply never had to care about not touching the polepieces with my thumb on my Yamaha BB and other basses I've tried, so my technique wasn't prepared.

What is the reason for the noise? Why doesn't this happen on all Jazz Basses with passive single coil pickups?

 

[RobbieK]

I assume that all of the instruments are grounded properly.

Unfortunately not. For some reason, Fender don't earth the exposed pole pieces in their pickups. Virtually all small pickup makers will (should!) do this if their designs feature exposed pole pieces.

So you can earth the pole pieces with copper tape that has conductive adhesive, but IME, this doesn't last very well. You are better using an overlapping combination of shielding paint and copper tape.

The other option is to reverse the phase of both pickups. The pole pieces will buzz far less if the inner windings (the start of the coil) is at earth.

The third factor is that no matter which end of the coil is at earth, you shouldn't get a buzz if you are also touching the strings. So check your bridge earth wire of course, but be aware that coated strings like elixirs and tape-wounds stop the string earth from working.

 

[DirkP]

Unfortunately not. For some reason, Fender don't earth the exposed pole pieces in their pickups. Virtually all small pickup makers will (should!) do this if their designs feature exposed pole pieces.

So you can earth the pole pieces with copper tape that has conductive adhesive, but IME, this doesn't last very well. You are better using an overlapping combination of shielding paint and copper tape.

The other option is to reverse the phase of both pickups. The pole pieces will buzz far less if the inner windings (the start of the coil) is at earth.

The third factor is that no matter which end of the coil is at earth, you shouldn't get a buzz if you are also touching the strings. So check your bridge earth wire of course, but be aware that coated strings like elixirs and tape-wounds stop the string earth from working.

Thanx a lot, maybe I didn't notice, but I feel secure that some Jazz Basses don't have that buzz even if I don't touch the strings and I'm sure the basses are not modified in any way. But maybe I'm wrong about not touching the strings. Happens mostly if I rest my thumb on the E-string and push a bit too hard towards the body.

 

[bholder]

Unfortunately not. For some reason, Fender don't earth the exposed pole pieces in their pickups. Virtually all small pickup makers will (should!) do this if their designs feature exposed pole pieces.

So you can earth the pole pieces with copper tape that has conductive adhesive, but IME, this doesn't last very well. You are better using an overlapping combination of shielding paint and copper tape.

The other option is to reverse the phase of both pickups. The pole pieces will buzz far less if the inner windings (the start of the coil) is at earth.

The third factor is that no matter which end of the coil is at earth, you shouldn't get a buzz if you are also touching the strings. So check your bridge earth wire of course, but be aware that coated strings like elixirs and tape-wounds stop the string earth from working.

In my experience, most stock exposed polepiece pickups exhibit this behavior (not unique to J single coils or even bass pickups). High end custom boutique replacement pickups maybe ground the polepieces, but most big manufacturers do not (at least, from what I've seen).

 

[Killed_by_Death]

I shielded the cavities in my Mexican Fender Blacktop & even then when I touched the pole pieces (humbuckers) I'd get noise, especially if the gain was turned up.
After the pole pieces were grounded it was silent, but I'm certain it wasn't my imagination that I lost some high end frequencies after grounding the pole pieces.

 

[DirkP]

Just had my '78 and my AVS '64 at home. The difference is huge. There's only audio at the left channel! The '78 has coated strings, but it doesn't matter, 'cause the difference is obvious when I just touch the polepieces without touching the strings. There is a little buzz on the '64 too, but much quieter. Could it be that the pickups in the '78 have become "microphonic"?

Don't listen loud!

Dropbox - IMG-0379.mov

 

[RobbieK]

Happens mostly if I rest my thumb on the E-string and push a bit too hard towards the body.

As I mentioned, if you are touching the strings and you get a buzz when also touching the pole pieces, it means your string earth isn't working. Either the wiring is faulty or the strings are coated.

 

[RobbieK]

The '78 has coated strings, but it doesn't matter, 'cause the difference is obvious when I just touch the polepieces without touching the strings.

Yeah, in that case as I mentioned, reserse the phase of both pickups, or earth their magnets. Either of these should fix the buzzy pole pieces man.

FWIW, if you take the covers off the pickups, you can usually see from the angle of the winding wire which end of the coil is which.

 

[DirkP]

Yeah, in that case as I mentioned, reserse the phase of both pickups, or earth their magnets. Either of these should fix the buzzy pole pieces man.

FWIW, if you take the covers off the pickups, you can usually see from the angle of the winding wire which end of the coil is which.

Thanks a lot. But out of curiosity: it still doesn't explain the huge difference between the '78 and the AVS '64 in the video.

 

[RobbieK]

it still doesn't explain the huge difference between the '78 and the AVS '64 in the video.

Sounds like the blue bass has earthed pole pieces and/or its inner windings are on the earth side of the circuit.
And the yellow bass does not.

As I mentioned, try reversing the phase of both pickups (on the yellow bass). To reverse the phase, you need to desolder the hot and earth wires, then solder the original hot wire to earth and the original earth wire to the centre lug of its volume pot. If you have shielded pickup leads instead of two single wires, you should remove the pickups and swap the phase at the eyelets instead of at the pots. If you can't solder or you don't have a good solder station, I suggest finding a reputable tech. (It's easy to damage the pickups with too much heat at the eyelets, and it's easy to damage the pots with too much heat on the casings or lugs.) But make it clear that both pickups need to be reversed. It's amazing how few techs understand this problem.