Partial coil-taps, the straight dope.

[Kobaia]

I just purchased a couple of Wilkinson bass pickups from China. Trusting these actually work, they are patterned on Musicman humbuckers, ala the Stingray, but without visible poles. I would like to coil tap them as I enjoy singlecoil bass pickup tones. However I hate the hum and buzz. Whilst I intend to shield the transplant instrument, I've read that you can route a coil tap through a capacitor (and resistor?) and keep most of the humbucking facility, retain a bit more bass end but still get a single coil tone. Is this true?

[drewfx]

If you split a humbucking PU by connecting a capacitor to ground at the point the 2 coils are connected together you effectively get a PU that is single coil at high frequencies and series humbucking at low frequencies. G&L L series basses are wired this way in series mode. You can find their schematics and wiring diagrams here:

G&L Schematics and Wiring Diagrams

The capacitor value determines the cutoff frequency between SC and HB. G&L uses .1 UF caps for this..

[Steve A.]

If you split a humbucking PU by connecting a capacitor to ground at the point the 2 coils are connected together you effectively get a PU that is single coil at high frequencies and series humbucking at low frequencies. G&L L series basses are wired this way in series mode. You can find their schematics and wiring diagrams here:

G&L Schematics and Wiring Diagrams

The capacitor value determines the cutoff frequency between SC and HB. G&L uses .1 UF caps for this..

Gibson has been using a .033uf cap instead of a jumper on the 2013 LPJ Pro coil cut switches and the result is a very thin sound, not a humbucker and not a single coil pickup either. Neither fish nor fowl...

I first read of using a cap instead of a jumper to ground in the 1980 edition of Donald Brosnac's Guitar Electronics. I tried to find the reference but its not listed in the index...

I was reminded my quest for schematics of his Tone-L-Filter and Tone-Q-Filter replacements for a tone control cap... any information on what is inside these magic boxes?

EDIT: here's a link to an MEF discussion which explains the science behind those filters without actually drawing up a wiring diagram or schematic.

http://music-electronics-forum.com/t29037/
Steve

[Kobaia]

If you split a humbucking PU by connecting a capacitor to ground at the point the 2 coils are connected together you effectively get a PU that is single coil at high frequencies and series humbucking at low frequencies. G&L L series basses are wired this way in series mode. You can find their schematics and wiring diagrams here:

G&L Schematics and Wiring Diagrams

The capacitor value determines the cutoff frequency between SC and HB. G&L uses .1 UF caps for this..

Am I right in thinking a .1 uF capacitor will hive off everything short of the fundamental? This could be good, as I'm after meatly single coil tones after all.

I built a passive A-B splitter/blender box about a year ago. I dug it out this last weekend and took it to practice without remembering what went into it. I built a decade switch into the box, with the option of having an inductor in our out the circuit after the caps. Good for those 'is it a wah?' '70s lead tones from guys like Michael Schenker.

[drewfx]

I forgot to note that traditionally MusicMan PU's have the coils wired in parallel and this approach with the cap is for when the coils are wired in series. Just wiring the coils in parallel may get you closer to what you're looking for. The cap between the coils in series approach gets a big fat series tone without losing the highs.

Am I right in thinking a .1 uF capacitor will hive off everything short of the fundamental? This could be good, as I'm after meatly single coil tones after all.

It's much fatter than SC tone - maybe more like a bigger P-bass tone. It may or may not be something you like. On a G&L, with their PU's it sounds huge and you wouldn't confuse it with a SC PU.

In terms of a cap value I would just try jumpering up various cap values - bigger values will lower the cutoff frequency between series and SC and smaller will raise it. Note that this also affects the frequencies where you get hum canceling too though.