Wiring Bartolini quad coils to Pope FlexCore with Coil Switch

[eightyearsapril]

(This is cross-posted from my build thread in the LC.)

I plugged the bass I built in to my amp last night and put her through the paces. Everything, with one caveat, sounded great. The EQ works well, with a lot of latitude for adjustment with the bass, both mids, and the treble controls. The coil switching knob works, as does the pickup pan, and the volume.

However.... there's something with the coil switch on the bridge pickup. With even a little bit of blend with the neck pickup, there's no issue, but when the bridge is isolated, I get little to no output when the coil switch is toggled (I think) in the single coil direction.

I had thought that something might be an issue, because the instructions I got from BBG back in December (before I ordered the pre-amp, but after I had ordered the my build thread in the LC pickups) were vague. Let me quote the email that Chris H at BBG gave me then, before I ordered the pre-amp:

*For Series:
- Black = Hot(This would go to the Pope input for pickup hot)
- Red & White = Linking wire. These get twisted together, soldered, and covered with heatshrink tubing to insulate them away from any other connections.
-Green & Shield(Shield is the bare braided wire) = Ground. These get twisted together, soldered, and go to input of the Pope balancer board at ground for each pickup.

*For Parallel -
-Black & Red = Hot. This would go to the Pope input for pickup hot
-White, Green, and Shield = Ground. These all get twisted together and input to the ground spot for pickup ground.

Now if you wanted to use the Pope Coil Split switch for a parallel-single coil switching scheme, then the Black from each pickup would go to hot, the red would go to the tap location, and green and shield would go to ground.​

I opted to go parallel-single coil switching, following the last paragraph. When I got the pickups, I noticed something weird, however: they weren't wired the same way.

The neck pickup had this configuration:

• Black
• Red/White (soldered)
• Green/Shield (soldered)

The bridge pickup, however, did not have the red and white wires soldered together:

• Black
• White
• Red
• Green/Shield (soldered)

When I wired up the Bartolini pickups to the FlexCore, I left the bridge white wire loose, while I followed the directions from BBG, and I also didn't unsolder the red/white from the neck pickup, so the connections on the FlexCore are:

1. SHIELDS GOUND: Bridge purple ground
2. BRIDGE PU GROUND: Bridge green/shield
3. BRIDGE PU TAP: Bridge red
4. BRIDGE PU HOT (+): Bridge black
5. NECK PU GROUND: Neck green/shield
6. NECK PU TAP: Neck red/white
7. NECK PU HOT (+): Neck black
8. BATTERY (+): unused, as I'm not using active pickups

Here's the instructions from the FlexCore manual (PDF):

And, here's how it looks in my crowded cavity:

I think, since the neck pickup is working fine, I need to emulate the red/white soldering of it on the bridge pickup, but the instructions from BBG are vague, as they don't mention the white wire at all with regards to the coil switching. Before I undo last work and get out the soldering iron again, however, I wanted to ask here.

Thanks!

 

[mikezimmerman]

From your description, the neck pickup came wired in series (the + [red] from one coil is connecting to the - [white] from the other coil), and the red/white wire pair is the coil tapping for series/single coil. (Not really "single", since the quad coil is really a pair of split-coils...)

For the bridge pickup, you are not grounding the black/white coil (the white - is not connected to anything). I would recommend just soldering the red and white wires together, just like on the neck pickup. It's not really clear from Pope's directions what exactly the "PU Tap" switch is doing, but from the way it works on the neck pickup, it's mostly likely just a SPST switch going to ground, so it wouldn't really work for parallel/single switching.

 

[eightyearsapril]

I would recommend just soldering the red and white wires together, just like on the neck pickup.

Thanks, that's what I figured I needed to do, but I wanted confirmation, as this is my first time building a bass and doing anything with the electronics.

It's not really clear from Pope's directions what exactly the "PU Tap" switch is doing

Here's how BBG explained it to me, in the same email chain last December (!) when I bought it:

The Pope system has an option for coil tap. It is really coil split, not coil tap, but that is what Mike called it so it stuck.

It only allows the pickups to go from Parallel to single coil as it is a 2-way switch. So if you wanted a different coil split or selection, like Series - Single Coil, or Series - Parallel - Single Coil, then you would want to use a different switch, and not the Pope coil tap accessory switch.​

I opted to use the Pope coil tap switch to minimize soldering. The FlexCore installation instructions are clear as mud on a lot of things, and the confusion with the Bartolini wiring hasn't helped.

Ideally, the switch would allow me to go from Series/Parallel to single (reversed split P-style) for the neck pickup, and Series/Parallel to single (J-style) for the bridge pickup, but that's probably not possible with the FlexCore pre-amp and switch I currently have.

 

[JustForSport]

Considering... I think I would wire it according to a Bart quad-coil option, which will give you the option of 'P' or 'reverse P' if you have Bart quads.
If you have Bart dual-coils w/ 4 coils, you may only have the 'coil-split' option, but you can use their diagram to feed the Pope pre'.
Whatever you do, you won't have a 'coil-tap' option, as the Bart coils aren't tapped.
And the Bart coil/wiring arrangement doesn't allow for 'Series/Parallel to single'- you have to choose 'Series/Parallel' or 'P' or 'reverse P' depending on your pickups.
BTW: it seems Bartolini has updated their new/revised site to include all the wiring diagrams form the previous site along with new diagrams.

 

[eightyearsapril]

Thanks, @JustForSport, but I'm not that ambitious yet.

I connected the red/white wires from the bridge pickup and reconnected it, plus the coil split switch, and all is (almost) well!

However, I have one last grounding, I think, issue to deal with: I get buzzing when I touch any of the knobs that goes away when I either remove my hand from the knob or touch a string with my other hand. I'm pretty sure I just need to check the ground wire under the bridge, but if there's something else I should look at, please let me know.

 

[JustForSport]

Seems your pots are not grounded to the same as the bridge. Be sure all grounds go to a common point and is connected to the jack ground terminal.

 

[eightyearsapril]

The issue is now resolved. The switch's circuit was touching the foil shielding, and probably caused a short. All is now well, and thanks for the help!