Correct wiring for 2 pups -> 2 volume pots -> jack out

[KiOgon]

My Frank Bello bass has low output from the bridge pup ( Fender samarium cobalt noiseless) compared to the neck pup SD SPB-3. I know it's a bit unusual having only a volume pot for each pup but - easy - NO!

I've bought a SD SJB-3b to swap for the scn, so upon removing the back cover I find the usual birds nest of black & white wires.
The white wire from each pup goes to #2 on each pot, blacks to pot bodies, (shown on diagram to #1)
White wire linking #1s on each pot, (shown on diagram to #2s)
#3 on each pot soldered to pot body, (shown on diagram not connected).
Jack socket wired white to #1 link, (shown on diagram to #2s link), black to body, black wire from each pot body + bridge bond to earth tag, + 1 extra black wire that goes into neck pup hole, (not shown on diagram at all).

2 or 3 days ago I emailed SD for info on using the 2 1/4 lbs together but no reply.

Checking the online Fender wiring diagram:- [url="http://www.fender.com/support/diagrams/pdf_temp1/basses/0130095306A/SD0130095306APg2.pdf"]http://www.fender.com/support/diagrams/pdf...0095306APg2.pdf[/url] shows different wiring, (as comments in brackets above).

Seymour Duncan website says:- "If two pickups sound thin and wimpy when used together, they’re out of phase with each other. If you’re combining your Basslines pickup(s) with Fender® pickup(s) in the same bass, you’ll need to reverse the black and white wires on the Basslines."

As mine could have been described as 'thin & wimpy' I tried reversing black & white = no discernible difference.

I phoned Fender UK & explained, then sent an email explaining again:-
"Hi Scott,
We spoke about the pup wiring on my Bello. The output of the bridge jazz pup SCN is not as good as the neck pup SD SJB-3 1/4 pound (standard), so I'm fitting a SD SJB-3b 1/4 pound to the bridge position.
Seymour Duncan website says:- "If two pickups sound thin and wimpy when used together, they’re out of phase with each other. If you’re combining your Basslines pickup(s) with Fender® pickup(s) in the same bass, you’ll need to reverse the black and white wires on the Basslines."
In the control cavity I find the original wiring is the mess I expected - both white wires from pups go to centre tag on each volume pot, both black wires to pot body. That is in contradiction with what is shown on Fender wiring diagram:- [url="http://www.fender.com/support/diagrams/pdf_temp1/basses/0130095306A/SD0130095306APg2.pdf"]http://www.fender.com/support/diagrams/pdf...0095306APg2.pdf[/url]

Hence my confusion! I have emailed Seymour Duncan via their website a few days ago regarding using the SJB-3b in conjunction with the standard SPB-3 neck but not got any reply.

Now I need the correct wiring information in a hurry - please can you get an answer for me - which way should the new SJB-3 be wired in?
Cheers,"

Their answer:-
"Hi John,
Thanks for your email.
I have had a word with a guitar tech about this and he has said that basically the Frank Bello bass is a ‘quirky’ model as it is a signature made to his specifications.
It is possible that due to the differences between this bass and a more standard version, the Seymour Duncan info you have is referring more to the standard version rather than the Frank Bello which was wired up in a more unconventional way! Unfortunately I cannot provide any further information on this as the guitar techs are unable to comment on how the SD pickups should be installed.
You said previously that you have the wiring diagram for this model (I have attached it again in case this is incorrect). I believe Seymour Duncan should be able to provide you with more specific details as to how it should be wired.
Sorry I cannot be of any further help on this.
Thanks,"

(The wiring diagram attached is identical).

I'm sorry this is long winded but could do with some technical advise please, I understand wiring & pots etc, (at least I thought I did!) Does it make any difference the way the pups are wired to #1 or #2 on the pots? Does it make any difference that #3s are soldered to the bodies?

It's all in bits at the moment, waiting for some copper shielding tape & some help please!

Thanks for reading
John

EDIT: I've just seen on performanceguitar.com >
# Shielding : $80.00~ !*80 bloody dollars*!
# Put Shielding Material inside of the Control Cavity
# (It makes your guitar noiseless)

Edited March 12, 2010 by KiOgon

[robocorpse]

The pickups sounding "thin and wimpy" would be both of them, not just one, if it was out of phase (one black/white pair reversed) so its not that.
The diagrams are correct, pickups should go to #1's and exit at linked #2's which feeds the o/p jack.
According to the wiring you describe in your own bass, the pots are wired wrongly, if you connect the pickup hot to tab 2, thats the wiper, and you are giving each pickup a variable resistance between hot and ground whenever you turn the pot. It will work, but it will vary the circuit characteristics. What you should be wired for is a constant resistance from hot to ground by connecting the pickup hot to one end of the track (tab 1), and the wiper picks up the signal somewhere along that line, so you get volume control, but the pickup side of the circuit stays at the same impedance. Maybe Franks bass is wired oddly, but I would think more likely it was goofed at the factory, and it might cause problems in the real world.
Tab 3 is always connected to earth, leave that alone.
You are obviously not averse to changing the wiring in the bass, so why not swap the #1 and #2 connections and see if that cures it? While you are doing that, it would be worth temporarily hard-wiring each pickup in turn DIRECT to the output jack, and see if there are still wimpy sounds coming from the bridge pickup, in which case you will know its knackered.
Only problem then is Fender will not honour the warranty as soon as you touch the solder joints. Catch 22...

Edited March 5, 2010 by robocorpse

[KiOgon]

Thanks robocorpse - very helpful cheers, I get exactly what you're saying about the wiper picking up along the track, sounds right.
'Goofed at the factory' indeed. No worries about the warranty - if only they got it right in the first place & customer service is as much help as a hole in your boat!
No problem changing things, I have a decent Weller iron & the right tools + skills for the job, I have already tried each pup direct to a jack socket & the bridge SCN is certainly lower lower output but I don't think it is faulty, just not as strong as the 1/4lb, causing a mis-match IMO pity Fender didn't fit 1/4lbs in both positions!
The behaviour of the pots was peculiar, the first 60 degrees or so of rotation had practically no effect, then at fully clockwise the volume & tone wasn't quite right, I had to back off both a little to achieve the max output & best tone. Used individually they're better but certainly not 'quite right' together.
No amp problems BTW, using my TE Boxer 65 - with settings the same as when using my '51P for comparison.

As soon as my copper tape arrives I'll get it back together, wired as you suggest & let you know.

Thanks again for your help, it's much appreciated,
John

[quote name='robocorpse' post='764665' date='Mar 5 2010, 01:01 AM']The pickups sounding "thin and wimpy" would be both of them, not just one, if it was out of phase (one black/white pair reversed) so its not that.
The diagrams are correct, pickups should go to #1's and exit at linked #2's which feeds the o/p jack.
According to the wiring you describe in your own bass, the pots are wired wrongly, if you connect the pickup hot to tab 2, thats the wiper, and you are giving each pickup a variable resistance between hot and ground whenever you turn the pot. It will work, but it will vary the circuit characteristics. What you should be wired for is a constant resistance from hot to ground by connecting the pickup hot to one end of the track (tab 1), and the wiper picks up the signal somewhere along that line, so you get volume control, but the pickup side of the circuit stays at the same impedance. Maybe Franks bass is wired oddly, but I would think more likely it was goofed at the factory, and it might cause problems in the real world.
Tab 3 is always connected to earth, leave that alone.
You are obviously not averse to changing the wiring in the bass, so why not swap the #1 and #2 connections and see if that cures it? While you are doing that, it would be worth temporarily hard-wiring each pickup in turn DIRECT to the output jack, and see if there are still wimpy sounds coming from the bridge pickup, in which case you will know its knackered.
Only problem then is Fender will not honour the warranty as soon as you touch the solder joints. Catch 22...[/quote]

[AlanP2008]

I hate to disagree here... but here it goes...

*Normally*, you'd wire a pup to the top of the pot, ground the bottom, and take the signal from the middle tag (the wiper). That is the conventional way to wire a volume pot for (almost) any occasion.

However, whenever you have *two* volume controls, you simply can't do that, because when one pot is turned right down, it is connecting the output signal directly to ground. That's fine when there is only one pot (it is what you want...), but when there is two volume pots, the signal from the wiper of the other pot is also connected to ground - that is to say, the two pots interact big time.

So the method used (electrically it's rather kludgy, but it works) is to connect the pup to the wiper, and take the output signal from the top tag on the pot (which sounds exactly like the way you were describing it was originally wired). So as one pot is turned down, it is progressively loaded down by the decreasing resistance to ground, but at the same time, the part of the track between the wiper and the top of the pot is progressively increasing the resistance to the output jack. In the end, the pup is shorted to ground, but the output isn't - the result is that there is little interaction between the two pots (well, there is interaction, but it is largely in your favour).

If you wire it like this - you could still end up with pups out of phase (which can be fixed by reversing one of them). You can usually tell they are out of phase if turning one volume pot down a bit actually causes the overall signal to get fatter and louder. If this isn't happening, and switching the wiring on one of the pups isn't helping either, then your problem lies elsewhere (ie. not phasing)...

Maybe this? In the (6-string) guitar world, single-coil pups are usuallly wired with a 250k volume pot, and humbuckers are usually wired with a 500k pot. A 500k pot on an SC *usually* sounds too bright, and a 250k pot on an HB *usually* sounds too dark. You should perhaps check what pot value is recommened for the pups you have (although mixing types, and hence pot values, is always a bit of a compromise...)

Hope this helps.

Alan

[KiOgon]

[quote name='AlanP2008' post='767634' date='Mar 8 2010, 09:46 AM']I hate to disagree here... but here it goes...

*Normally*, you'd wire a pup to the top of the pot, ground the bottom, and take the signal from the middle tag (the wiper). That is the conventional way to wire a volume pot for (almost) any occasion.

However, whenever you have *two* volume controls, you simply can't do that, because when one pot is turned right down, it is connecting the output signal directly to ground. That's fine when there is only one pot (it is what you want...), but when there is two volume pots, the signal from the wiper of the other pot is also connected to ground - that is to say, the two pots interact big time.

So the method used (electrically it's rather kludgy, but it works) is to connect the pup to the wiper, and take the output signal from the top tag on the pot (which sounds exactly like the way you were describing it was originally wired). So as one pot is turned down, it is progressively loaded down by the decreasing resistance to ground, but at the same time, the part of the track between the wiper and the top of the pot is progressively increasing the resistance to the output jack. In the end, the pup is shorted to ground, but the output isn't - the result is that there is little interaction between the two pots (well, there is interaction, but it is largely in your favour).

If you wire it like this - you could still end up with pups out of phase (which can be fixed by reversing one of them). You can usually tell they are out of phase if turning one volume pot down a bit actually causes the overall signal to get fatter and louder. If this isn't happening, and switching the wiring on one of the pups isn't helping either, then your problem lies elsewhere (ie. not phasing)...

Maybe this? In the (6-string) guitar world, single-coil pups are usuallly wired with a 250k volume pot, and humbuckers are usually wired with a 500k pot. A 500k pot on an SC *usually* sounds too bright, and a 250k pot on an HB *usually* sounds too dark. You should perhaps check what pot value is recommened for the pups you have (although mixing types, and hence pot values, is always a bit of a compromise...)

Hope this helps.

Alan[/quote]

Yes - thanks Alan, great help ta. I'll read that again & I think a bit of trial & error is coming my way

Cheers,
John

[KiOgon]

Finally back together & sounds amazing Exactly how I hoped it would + Looks fantastic
Thanks again to Alan - his info was spot on - Cheers I o u 1

After all my work, I'm wondering if that's why it was sold in the first place, 'cos it's now sounding a hundred times better!