How can I wire a pot like reverend does to make a humbucker sound like a single coil?

[EffectsGuru]

How can I make a pot (potentiometer) that functions like it does on Reverend Guitars? I havn't been able to open one up and look... but I would really like to do this on a guitar at some point instead of or in addition too a tone control. The pot is wired so that it can make a humbucker sound like a P-90 or a this single coil, it's pretty amazing actually, it's unique though, not exactly the same as going from humbucker to P-90, and I believe this has been used on effects pedals, I just wasn't sure how to apply it to a guitar. It would also be a nice thing to add to the list of guitar wiring methods that I currently know, I mean how many luthiers are familiar with this and can offer that to their customers? Not many I would imagine. So if anyone out there knows how it's done, please let me know... or better yet, open the back of your Reverend up and take a picture for me, I would really appreciate that. Thanks.

[cbarrow7625]

Are you referring to their "Bass Contour" control? If you are, it sounds to me like they are using a 250k or 500k pot with a cap around it in series with the signal just forming a simple high pass. I have never heard one of their guitars, I'm just guessing from reading the lit on their website.

Since that control appears to be on guitars with humbuckers or single coil P90's I am guessing that it does not do anything to the pickups directly unless Reverend has a special 1/2 coil tap on their pickups. If that is the case, you could do something similar to a standard humbucker by wiring the center tap to a pot to ground (like a tone control) to gradually change the pickup from humbucking to single coil. It would likely require a smallish pot (less than 100k) to work smoothly.

I have tried a cap around a pot in series to roll off bass but never found it terribly useful. They must be doing something more than that.

Not a direct answer to your question but hopefully it gets you going in the correct general direction.

[David Schwab]

Peavey used to have a tone control that split a humbucker into a single coil. They had a patent on it too.

If it's being done with a cap, a .0047uF in series should do it using a setup as cbarrow7625 described.

[cbarrow7625]

I forgot about the cap. Using the cap allows you to basically get a single coil tone without ruining the low frequency hum cancelling effect from the pickup. I wasn't aware that peavey had a patent on it. Is it possible that that patent is still active? How long ago was that? It is a really useful 'trick' that I have used a couple of times over the years in various guitars of mine. I had actually forgotten all about it until this thread. Now I want to try it again!

[Mark Hammer]

Peavey used to have a tone control that split a humbucker into a single coil. They had a patent on it too.

If it's being done with a cap, a .0047uF in series should do it using a setup as cbarrow7625 described.

Check here: http://natcade.tripod.com/schems/Peavey/t-40_t-60.gif

Note that, as the tone control is rotated clockwise, the resistance between the junction of the two coils and ground is reduced, until finally the midpoint between coils is fully grounded. Rotating counterclockwise, the coil-junction becomes increasingly "ungrounded" until there is finally a .022uf cap going from the volume pot input straight to ground, essentially mimicking a standard tone pot set to full treble-cut.

What I've done several times is simply use a larger-than-normal value compensating cap in the volume pot. Typically, one would expect to see compensating caps on a 500k volume pot in the under-1000pf range. If you use a cap with a value around, say 1500-1800pf, the treble-retaining qualities one gets out of a volume pot as you turn down are replaced with enough mids-and-treble retention that the volue pot seems to behave like a bass-cut control. If I had a 4-knob/dual-humbucker guitar, I suspect what I'd do is wire up the bridge volume in that way, with "normal" wiring of the bridge tone control, using a 6800pf cap. Wiring up the neck pickup in the Peavey T-60 manner, in tandem with the suggested bridge wiring would get you a pretty broad palette of tone colours to choose from.

Note that where the Peavey tone control essentially loses you hum-rejection as you fade from dual-coil to single coil, the bass-cut control maintains humbucking effect at all times.

[JoeM]

Mark,

The link didn't work, but I uploaded a schem.

[David Schwab]

I've done the Peavey thing on a few guitars. Another interesting trick is to use a .02 cap between the series connection at the humbucker, and the pot. I got that trick from Bill Lawrence. It does a frequency dependent split, so the highs are single coil sounding, but you still get some hum cancelation.

The other trick, which is wiring up a passive bass cut control to simulate a single coil works like this G&L circuit. If you really wanted to get fancy, you could wire up a dual gang pot like a Fender TBX, using the 250K half as a treble cut tone control, and the 1M half as the bass cut.

I'm not sure how the taper would be, but it could be a cool control to go from one tone to the other.

I used to use the bass cut cap trick to simulate single coils with EMG humbuckers.