P/J wiring issues

[NoirBass]

I've recently become the proud owner of a Fender Cowpoke. It originally had stacked vol/blend and treble/bass controls along with an onboard active preamp. I'd like to rewire it as a passive P/J. Having tried a few configurations that lead to loud hum, I finally settled on this:

http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=std_jazz_bass

Which seems to work great (no hum) but when I roll up the volume pots to about 90% I get a massive volume drop off and lose all the low end.

Furthermore if I have any blend of the two pickups I seem to get odd results, the only time I get what I'm expecting is with each pickup soloed.

I'm tempted to go for Vol/blend/tone instead:

http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=p_j_bass_blend

would that cure my issues?

all help gratefully received.

[bremen]

Your pickups are out of phase. Swap the wires on one of them.

[NoirBass]

Hi bremen, Thanks for the reply.

[quote name='bremen' timestamp='1349811519' post='1830942'] Your pickups are out of phase. Swap the wires on one of them. [/quote]

Forgive my ignorance, do you mean swap the locations of the black and white wires coming off the pickup?

[KiOgon]

[quote name='bremen' timestamp='1349811519' post='1830942']
Your pickups are out of phase. Swap the wires on one of them.
[/quote]
+1 Most likely!

IIRC the SD P/J blend circuit works better without the ground to the blend pot body, apart from that both diagrams are good.

[bremen]

[quote name='NoirBass' timestamp='1349812588' post='1830977']



Forgive my ignorance, do you mean swap the locations of the black and white wires coming off the pickup?
[/quote]

that's right. just the one pickup; if it hums, swap them back and try it on the other pickup.

[NoirBass]

Cheers guys, that sorted it.

I will wire it with the blend eventually, but for now I'll stick with the Jazz config.

My next issue it to source a dual concentric pot for volume and tone, the originals are 1M and have extremely long shafts.

Does anyone know where I can get a 250k stacked pot with a long shaft?

[bremen]

Try www.thomann.de/gb

[iiipopes]

NOT NECESSARILY OUT OF PHASE

Impedance drop leading to volume drop when full on in a VVT configuration is common to all 2-pickup basses. Yes, you can switch the wires on the J bridge pickup, and it does seem to have helped a little bit, but it's not a perfect solution, especially since the J is a single coil and the P is effectively a humbucker. So with both on, one coil of the P pickup is getting reinforced while the other is not, resulting in an imperfect setup.

Two solutions:
1) Get a humbucking J bridge unit to match the P, like a DiMarzio UltraJazz or similar, and/or
2) put a .01 capacitor inline from the hot lead of the bridge pickup to the wiper on its volume pot in conventional VVT wiring. There's not much fundamental signal coming out of the bridge pickup anyway, and this will help with the impedance drop/comb filtering issues.

Edited October 10, 2012 by iiipopes

[bremen]

[quote name='iiipopes' timestamp='1349877481' post='1831653']
the J is a single coil and the P is effectively a humbucker. So with both on, one coil of the P pickup is getting reinforced while the other is not, resulting in an imperfect setup.


[/quote]

Not true; yes, the P is a humbucker but the polarity of the magnets is reversed between the two halves so although the coils cancel hum from an external source, the currents generated by the vibrating strings are in phase. I learned this the hard way when I acquired a P pickup that didn't have the reversed magnets; works fine as a P but when the original owner tried it in his PJ he experienced the effect that the E and A were in phase with the J pickup, the D and G were out and consequently cancelled. A properly wired PJ works absolutely fine (there's a midrange scoop on mine as expected, but plenty of bass with both P and J on full).

Anyway, :

[quote name='NoirBass' timestamp='1349864167' post='1831394']
Cheers guys, that sorted it.


[/quote]

[NoirBass]

[quote name='iiipopes' timestamp='1349877481' post='1831653']
NOT NECESSARILY OUT OF PHASE

Impedance drop leading to volume drop when full on in a VVT configuration is common to all 2-pickup basses. Yes, you can switch the wires on the J bridge pickup, and it does seem to have helped a little bit, but it's not a perfect solution, especially since the J is a single coil and the P is effectively a humbucker. So with both on, one coil of the P pickup is getting reinforced while the other is not, resulting in an imperfect setup.

Two solutions:
1) Get a humbucking J bridge unit to match the P, like a DiMarzio UltraJazz or similar, and/or
2) put a .01 capacitor inline from the hot lead of the bridge pickup to the wiper on its volume pot in conventional VVT wiring. There's not much fundamental signal coming out of the bridge pickup anyway, and this will help with the impedance drop/comb filtering issues.
[/quote]

Thanks for the info iiipopes, I was thinking of eventually getting a Seymour Duncan STK-J2b to go with the SD Quarter Pounder that is in there.
I'll stick a .01 cap in there until then. The bass sounds a lot better having reversed the bridge pickups wires, but there is still some odd things happening just before the pot is set to maximum.


[quote name='bremen' timestamp='1349865196' post='1831411']
Try www.thomann.de/gb
[/quote]

Can't see anything on there that fits the bill, closest thing I can find is:

http://www.allparts.uk.com/online-shop/guitar-bass-parts/electronics/250k-pots/stacked-concentric-pot-250k250k-metric-p-4072.html

or these and wire the volume to the 500k:

http://www.allparts.uk.com/online-shop/guitar-bass-parts/electronics/miscellaneous-pots/control-concentric-250k500k-audio-solid-shaft-p-4566.html

[iiipopes]

[quote name='NoirBass' timestamp='1349879159' post='1831691']
Thanks for the info iiipopes, I was thinking of eventually getting a Seymour Duncan STK-J2b to go with the SD Quarter Pounder that is in there.
I'll stick a .01 cap in there until then. The bass sounds a lot better having reversed the bridge pickups wires, [b]but there is still some odd things happening just before the pot is set to maximum[/b].[/quote]

Yes, indeed. That is [i]exactly [/i]what I'm talking about. The only drawback is that you might have to raise the pickup slightly, as there may be a slight loss in overall volume from the capacitor functioning as a high-pass filter.

I've tried the SD stack. It was indistinct in the low register on my bass, and that is the nature of a conventional non-isolated stack pickup. To get enough bass response from the two coils tending to cancel each other out, it has to be overwound, with the resulting loss of definition. I'd go with DiMarzio J or UltraJazz, Fralin end-to-end or Aguilar end-to-end, or whatever may be similar on your side of the pond, with preference for the UltraJazz to match the SD QP P-pickup.

Bremen - I'm glad you have had a better experience with your P-J single coil than I did. With all the electrostatic noise and hum that can be generated on stage with lighting levels, both incandescent and otherwise, as well as multiple earth's from the amps and PA equipment, to say nothing of fluorescent or transformer noise, I'll never play a single coil pickup on stage again.

Edited October 10, 2012 by iiipopes

[NoirBass]

Cheers again for your respective input.

On closer inspection it seems that with either pot set to maximum, turning the other only really kicks in the pickup at about 90 - 95%.

I'm using two 250k CTS pots and a .047 Orange drop cap.

Edited October 11, 2012 by NoirBass

[Noisyjon]

Just to resurrect this one a bit - I put a set of Nordstrand P/J pickups in my bass (with the split coil jazz) and had the out of phase thing going on with both volumes up full. I reversed the wiring on the Jazz pickup and Robert is my Father's Brother!

Thanks Guys for the indirect help.

Cheers,
Jon

[NoirBass]

[quote name='jonthebass' timestamp='1366064758' post='2048057']
Just to resurrect this one a bit - I put a set of Nordstrand P/J pickups in my bass (with the split coil jazz) and had the out of phase thing going on with both volumes up full. I reversed the wiring on the Jazz pickup and Robert is my Father's Brother!

Thanks Guys for the indirect help.

Cheers,
Jon
[/quote]

No Problem, glad to be of indirect service.


[quote name='NoirBass' timestamp='1349969997' post='1832926']
Cheers again for your respective input.

On closer inspection it seems that with either pot set to maximum, turning the other only really kicks in the pickup at about 90 - 95%.

I'm using two 250k CTS pots and a .047 Orange drop cap.
[/quote]

And for the sake of completeness, having double checked my above observations it seems everything is working as it should not as I described above.

Incidentally there was quite a lot of earth hum with this setup so I eventually got a split single coil for the bridge pickup and that sorted it.

Good luck with your P/J's

Edited April 18, 2013 by NoirBass

[Twigman]

I think this might be the problem with my Warmoth P/J.

I got so frustrated by it that I went out and built another Warmoth active P instead! An expensive fix for what is likely to be a simple problem.


Will get the soldering iron out asap.

[Ghost_Bass]

This is the kind of stuff that makes me like the stacked, individual vol/tone for each pickup, configuration ('62 stacked J wiring). All is needed are two resistors on the signal going from each pot to the jack to avoid crosstalk between pickups and you're set to go. I find it a very versatile config especially if you stick a .10uf cap on the P and a .022 or .033uf cap on the J.