Wunkay Mod, SERIES HB - Single Coil - OMG

Bass mods, tweaks, and the like are home in here. Got an Evil Experiment to share? Pull up a keyboard and have at it!

The EBA is hosted by deltafred, a UK based pro player and electronics guru.

No sales or advertisements, no matter how well veiled, are permitted - not even a pointer elsewhere.

Moderator: deltafred

Re: Wunkay Mod, SERIES HB - Single Coil - OMG

Postby Ken Baker » Sat Nov 09, 2019 2:31 pm

derick wrote:Please bear with me, I am trying to wrap my head around this.

Is this schematic correct?

Yes, but not necessarily easy to read unless you're used to reading schematics. Wiring diagrams, which represent physical parts and their locations, are easier to work with. See below.

Another thing that I don't understand, in OMG mode I am able to disconnect the .1UF capacitor and get full series humbucking. But it looks to me from the schematic that doing that would break the path and completely remove the black/white pickup coil from the circuit.

So long as the shorting lead from switch lug 3 to switch lug 6 is in place, all that removing the OMG cap does is stop the treble cut that it provides. As you found, that leaves you with straight-up series humbucking mode.

That isn't what is happening, but I don't understand why.

It has to do with where in the signal path we sink off the treble. With the OMG cap in that location on the switch (or equivalent), the treble sink is only applied to one of the coils. The other coil remains full frequency. As an aside, this leaves the two coils a bit impedance unbalanced, which is why you get a little single coil noise with OMG mode.

EDIT--- Okay, so if the OMG cap is removed, then the 3 pin (black pickup wire) is still connected to the 2 pin (yellow pickup wire) and we must get series HB from that?

Okay. I found this drawing from Paul in a pile of papers yesterday while I was looking for something else. It's more of a wiring diagram than a schematic. It also "proofs" the signal path for the three switch positions. Note that switch orientation is not important for this implementation. For purposes of this discussion, the upper-left switch lug is number 1 and the upper right lug is number 4; lower left is 3 and lower right is 6. This may be a bit more helpful to you.

Click the images for a full sized PDF.

User avatar
Ken Baker
Site Admin
Posts: 4549
Joined: Sat Oct 10, 2009 10:33 am
Location: 12 miles WSW of Fender Ave. Fullerton

Re: Wunkay Mod, SERIES HB - Single Coil - OMG

Postby derick » Sat Nov 09, 2019 4:26 pm

Yes, that does make sense, and I think it does match up with Paul's schematic that I posted. Slightly different than the stock 1K circuit, but does exactly the same thing.

So, the secret to SeriesHB is bridging the black pickup wire to the yellow, and making sure that the black wire never grounds, except by forcing it through the other coil. Easily done with a push-pull vol pot, more difficult when two of your three switch positions bridge the black coil wire to ground...
User avatar
Posts: 134
Joined: Sat Aug 06, 2011 10:31 am


Return to The Experimental Bass Association

Who is online

Users browsing this forum: No registered users and 2 guests