Dual Coil Bass Pickup - Noise

[Lucky13]

Hi, long time lurker, first time poster..

I've made a number of pickups over the last couple of years and have been really pleased with the results, however I've run into a problem recently when attempting to make my first dual coil bass pickup.

The pickup is basically 2 Jazz style coils (2 magnets per string) in one cover, wound with 42AWG wire, with each coil measuring 8k. The pickup works (and sounds good) but even though the coils are RWRP and the bass is fully shielded, I'm getting a lot of noise. If I touch a ground point (back of pot, jack socket, etc), then the noise disappears. I know this would normally suggest a shielding issue but as I said, it's very well shielded.. it appears to be an issue with the pickup itself, but I have no idea what I could of done wrong.

Any help much appreciated.

[Helmholtz]

Sounds like electrical ("static") as opposed to magnetic noise.
You say the bass is "fully" shielded, but are shield (foil, paint etc.) as well as strings and bridge actually grounded?
Use your Ohmmeter to verify.

Is the jack correctly wired?

Are the PU coils wired in series or parallel?

Best post pictures.

[Lucky13]

Sounds like electrical ("static") as opposed to magnetic noise.
You say the bass is "fully" shielded, but are shield (foil, paint etc.) as well as strings and bridge actually grounded?
Use your Ohmmeter to verify.

Is the jack correctly wired?

Are the PU coils wired in series or parallel?

Best post pictures.

The control cavity and pickup cavity have been shielded with paint (with a wire to connect them together), the jack is wired correctly and the bridge/strings are grounded.

I've checked everything with a multimeter to check ground connections and conductivity of the shielding paint and everything passes the test. I originally had a mini toggle wired to switch between series/parallel, same problem in either mode.. apart from obviously being louder in series. I've since wired it directly to the jack, to eliminate any issues with the switch, as well as trying another jack socket, still no luck. Everything points to the pickup itself being the culprit.

[big_teee]

HI
Pictures might help us see what you've got.
T

[Lucky13]

HI
Pictures might help us see what you've got.
T

I can't do photos at the moment, I'm afraid my phone's camera isn't working after being dropped one time too many.

I should also add that I've checked that it's not an issue with the cable, or amplifier. I've also used a different mains outlet to take that out of the equation.

[big_teee]

So more info on the pickup.
Are both jazz pickup coils wound in same direction?
You said one coil reverse wound?
One coil has magnets north up, and one south up?
Finish lead of one pickup wired to the start of the other pickup?
Or finish lead of one wired to the finish of the other?
Let's start at the beginning and establish how it is built?
T
**Ideally if reverse wound, I would strap them Finish to start.
The coil with the start lead would be grounded, and the finish of the other coil would be connect to output.
If you had a way to ground the magnets that might help

[Lucky13]

So more info on the pickup.
Are both jazz pickup coils wound in same direction?
You said one coil reverse wound?
One coil has magnets north up, and one south up?
Finish lead of one pickup wired to the start of the other pickup?
Or finish lead of one wired to the finish of the other?
Let's start at the beginning and establish how it is built?
T

Yep, one coil is wound CW the other is CCW. One is south up, the other north up. It's wired with a 4 conductor cable, to enable a mini toggle to switch between series/parallel. The pickup functions fine in both modes (apart from the noise), both coils are working, no phase issues.

Edit: Poles are grounded with foil and connected to the bare wire.

[big_teee]

I would still like to see how it is wired.
Wiring is critical, and the more wire & switches you have, the more path for noise.
When you say the poles are grounded?
Have you used a multi meter on ohms and read from top of each magnet to ground.
Is all wiring shielded and no loose wiring?
Wire from jack direct to volume switch.
If you really won't to fix it, divide and conquer.
Wire humbucker direct to jack with 2 wire with grounded shield.
If it is quiet like that, then start putting the circuit back together until it gets noisy again.
Like Napoleon, divide and conquer!
GL,
T

[Lucky13]

That's exactly what I've done, I've wired it straight to the jack socket (I've also tried another jack socket just in case). I use the same colour code as Seymour Duncan.. black for the start of north coil, white for north finish, green for south start, red for south finish. So wired to the jack = black for the signal, green/bare to ground and red/white soldered together and taped off.

I've checked the poles with the multimeter and no issues there.

Thanks for all the suggestions by the way, I appreciate the help

[mozz]

I've made 1 set of jazz pickups before, but i have to ask, why are you grounding the magnets?

[Helmholtz]

When you touch grounded points with your finger, two things happen:
1) Noise voltages on your body get shorted to ground, so no longer cause interference and
2) your grounded body acts as an additional shield.

The fact that this stops the noise, shows that your bass shielding is insufficient for your environment and that the noise is not of magnetic nature.
(Of course, 100% electrical shielding is hardly possible.)

[Lucky13]

When you touch grounded points with your finger, two things happen:
1) Noise voltages on your body get shorted to ground, so no longer cause interference and
2) your grounded body acts as an additional shield.

The fact that this stops the noise, shows that your bass shielding is insufficient for your environment and that the noise is not of magnetic nature.
(Of course, 100% electrical shielding is hardly possible.)

I agree, that would be the logical answer.. however in this case the instrument couldn't be shielded to a higher degree. Everything that can be shielded has been either been painted or had copper foil applied and I've checked everything thoroughly with a multimeter.

[Lucky13]

I've made 1 set of jazz pickups before, but i have to ask, why are you grounding the magnets?

This explains it better than I could http://www.audereengineering.com/FAQ_PUMag_Gnd.htm

[Helmholtz]

It is essential that each single part of your shielding makes good contact with the ground at the jack.
E.g. a non grounded piece of shielding foil can actually increase interference.

Any strong interference sources like dimmers, phones, neon lamps around?

Did you compare with other instruments or PUs in the same room?

[Lucky13]

It is essential that each single part of your shielding makes good contact with the ground at the jack.
E.g. a non grounded shielding foil can actually increase interference.

Any strong interference sources like dimmers, phones, neon lamps around?

Did you compare with other instruments or PUs in the same room?

There's very little that would create a noisy environment, no dimmers or other electrical equipment. Turning the 2 strip lights off in the room creates a minor reduction but it's still way noisier than it should be.. for example, it's far noisier than any of my single coil equipped guitars are in the same room w/ same amp.