Spin-a-parallel control, VCC mods or alternatives?

[Yogi B]

Separated from frets' Spin-a-Split with a tone cap thread.

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I wonder if anyone here has experimented with a spin-a-parallel type control (the Washburn VCC, probably being only example I've ever seen). The main barrier to entry being the requirement of a dual-gang pot, ideally with both elements being reverse-log taper (Washburn used linear) — though you could use log and have the control work in the opposite direction. The upside is that the output will be hum-cancelling throughout the entire range of the control, assuming both coils always have equal loading applied (which is true of the VCC).

For reference:

[frets]

Yogi,
I will try this mod given I have dual gang push pulls and it sounds very interesting. Thank you😺

[Yogi B]

Jun 19, 2021 17:59:56 GMT -5 frets said:

Yogi, I will try this mod given I have dual gang push pulls and it sounds very interesting. Thank you😺

I was just curious if there was an official GuitarNuts2 'better way to do it'.

The design of the VCC causes the dullest and lowest output setting to occur at the midpoint of the pot's sweep (with the default linear taper) and most of the volume change to be located between 10 (full series) and about 7:

Switching to a reverse log taper helps the sweep, but does nothing to help the tonality of the in-between settings actually fall between series & parallel:

Something that could be done is to add some kind of treble bleed between the wiper & terminal 3 of the lower pot, this would help maintain treble mid-sweep but comes with the caveat that what ever is placed in this position will ultimately be placed in parallel with the fully parallel setting. In other words we'll have a mediumish resistor and smallish capacitor loading the parallel combination of coils, lowering the resonant peak of this setting both in terms of amplitude & frequency, bringing it (electrically) closer to the response a single split coil.

So really what I'm wondering is: is it possible to avoid this compromise?

However, for now I'm willing to double down on the idea of a loaded parallel combination standing in for a true split coil. Rearranging the upper potentiometer a little (and switching the rotation direction for log pots), we can add optional resistors/trimpots to tune how the parallel combination will load other pickup (the two 5k6 resistors in the below image). For example: if we choose the value of those resistors to be equal to the resistance of the individual coils, then when combining the bridge & neck in parallel the loading effect of, say, the neck pickup set to parallel upon the bridge pickup set to series would more closely approximate that of a split neck.

Schematically this version looks like this:

And the response between parallel & series, something like this (again, note the reversed colouring indicative of reversed direction):

[Deleted]

Guessing the different colours on the graph is the pot moving . (Key)
Driving me nutz with the Dark Blue being the same in both the Top&Middle Graph when you change the Pot Type to C500K

All the way to 3 its RIGHT + LEFT and to 1 its RIGHT x LEFT . I keep looking at the 1nF and 120K as a bleed system.
5K6 you wanted as a TRIM Pot depending on the Pickup!

What software you use to mock this up.

[frets]

Yogi😸,

Thank you for mocking this up. I am going to try it but I’m confused about whether a standard dual gang push pull is the correct pot?

[newey]

Yogi B-

This idea probably should get its own thread, so we can find the discussion in the future.

[Yogi B]

Jun 20, 2021 5:28:03 GMT -5 @angellahash said:

Guessing the different colours on the graph is the pot moving.

Correct, the bright red plot is with the pot fully clockwise (on 10) and each additional line in order of the spectrum represents a 10% turn down to purple at 50% wherein the cycle then repeats with darker colours, finishing up at dark blue which corresponds to fully counter-clockwise or zero.

What software you use to mock this up.

LTspice.

Jun 20, 2021 18:20:38 GMT -5 frets said:

I am going to try it but I’m confused about whether a standard dual gang push pull is the correct pot?

If by standard you mean logarithmic then yes, my version is drawn up to get the best taper from a log pot.

(For the original VCC drawing you'd need to swap terminals 1 & 3, if using a log pot.)

[Deleted]

its possible to turn off the bleed system when you want it to
just need to know what point you want it changing
could flip this bleed to the output as it comes up towards being in Parallel and cut it out at any point within series

just never see a bleed on that side of things
if done right you could force it to be
One Pickup ,Other Pickup, One Pickup with Other Blending in series with it till fully in Series ... or One Pickup with Other Pickup being Volume controled in