Series wiring with separate volume pots?

[Cernael]

So, basically, if you have two different pickups, and a switch that changes them from series to parallel wiring; is there a sensible way to have individual volume pots for the pickups?

My initial scribbling suggests that, when the p'ups are in series, if you place a pot in parallel with each p'up, with the pot at zero, you essentially short out the p'up, letting the other one sound.

I'll draw up a schematic, hang on.



Sorry 'bout the colour.

Lower left & upper right are p'ups, lower right & upper left are pots, centre thingie is an on/off switch, that ought to select between series/parallel, down is connected to ground, up to hot.

One concern is, I think in series, the pots are connected the wrong way around for audio taper (as max resistance then means max volume, while in parallel, minimum resistance is max volume)...

Anyway, comments?

[bnt]

Nah - I think you're looking at more complex wiring to get the effect you're after. If you look at the diagram on [url="http://www.buildyourguitar.com/resources/tips/serpar.htm"]this page[/url], it's labeled as a humbucker coil series/parallel switch, but the principle is the same. Just don't get the phase wrong: it will help to remember that both "hots" go to one side of the switch, after standard volume controls, and both grounds to the other side.

Edited August 13, 2008 by bnt

[Cernael]

Ah, but that one doesn't include the volume pots. They were what I began to ask for, before I got carried away.

Let's start at the beginning; individual volume pots in series wiring. Ignore the switch for a while.

If a pot is wired in parallel to a pickup, lowering its resistance is essentially the same as shorting the pickup to itself, right? Following the path of least resistance, most of the signal goes through the pot when it's set to zero resistance, and more goes to the amp when the pot's at full resistance?

Since I can't be bothered making another schematic, here's some shorthand:

(neck pickup<parallel>volume pot 1)<series>(volume pot 2<parallel>bridge pickup)

There's pickups in parallel with one volume pot each, and two such pickup+pot aggregates wired in series.

A standard jazz wiring, excluding the tone pot, would, in the same improvised shorthand be:

(neck pickup<series>volume pot 1)<parallel>(volume pot 2<series>bridge pickup)

Now, assuming both these versions work somewhat satisfactory, an on/off switch as wired in my above schematic ought to toggle between them, unless I've made a mistake in dreaming this up. Have I?

I realize that there probably will be some issues with crosstalk, i.e. both pots will influence the volume of both pickups so some degree, in the series version, but I don't know what to do about that, don't know if anything CAN be done about that, if you're going to still be able to control the volume of each pickup.

The issue, as I see it, with connecting the pots in series with the pickups, and then the pickups+pots in series, too, is that the wiring will be something like
(bridge pickup<series>volume pot 1<series>neck pickup<series>volume pot 2)
i.e., both pots change the volume of both pickups equally much, and there is no way to change the balance between them.

Hope that's clearer.

And yes, phase is another thing to consider; I haven't started worrying about that yet, though.

Edited August 13, 2008 by Cernael

[bnt]

[quote name='Cernael' post='261893' date='Aug 13 2008, 08:27 PM']Ah, but that one doesn't include the volume pots. They were what I began to ask for, before I got carried away.
...
Hope that's clearer.[/quote]
Not really - a discussion like this really needs pictures! It's late, but let me see if I can throw something together with Visio.

Firstly, I've had a go at redrawing your original diagram: does this look right?
[attachment=12100:S_P_1.gif]

If so, I think I see where you're coming from. Forget what I said about standard volume controls - they shunt the output to ground and aren't going to work here.

Let's say you have the switch closed, so the pickups are connected serially. With both pots at maximum (highest resistance), you'd have both pickups at full, as you'd expect:
[attachment=12101:S_P_2.gif]
(If a pot was turned to the other side, that would bypass the pickup, silencing it.),

However, if you were to flip the switch at that point, you'd have this:
[attachment=12102:S_P_3.gif]
which would be a problem. Each pickup would be in [i]series[/i] with the potentiometer at max resistance, and after that the pickup-resistor combinations are in parallel. In effect, the volume controls are reversed, and you'd need to turn each all the way around if you wanted any sound from either pickup. (That's my reading of it.)

The idea I had was to combine that diagram I linked to before with volume pots in series, like this:
[attachment=12104:S_P_4.gif]

A bit more complicated, I know, a DPDT switch and more soldering, but it's the best I can do at 2AM! I'll have another look tomorrow.

[Cernael]

Yeah, you understood me right.

Good pics, BTW.

The problem with the last one, as before is that the pots aren't individual volumes. I THINK they actually need to be connected to the pickups in parallel, when the pickups are in series.

Another strangeity with my starter idea, is that when you flip the switch, yoou change which pot controls which pickup; when you think about it, that combines with the issue about resistance =/= volume that you described, in an almost intuitive way: with one pot at full and the other at zero, it's the same pickup that's soloed, no matter what the switch position.

Still, stereo pots might be a good idea. That'd solve the issue about reverse tapered audio pots, too. Don't know how many poles you'd need on the switch, though.

[bnt]

[quote name='Cernael' post='262311' date='Aug 14 2008, 12:05 PM']The problem with the last one, as before is that the pots aren't individual volumes. I THINK they actually need to be connected to the pickups in parallel, when the pickups are in series.[/quote]
I think you're probably right about that, and I'll look in to that later if I can. It was 2AM, that's my excuse and I'm sticking to it.

PS: if you have access to Microsoft Visio, I'm finding it's a great tool for this, though I don't know it that well yet. For example, you can change the position of a switch or pot by changing a parameter - I didn't have to re-draw anything once I got the basic layout right.

[Cernael]

Think I have the solution; it requires two stereo pots, and one 4pdt switch. I'll try to draw it up comprehensibly. Stay tuned...

Here it is. The middle two poles are the standard dpdt series/parallel switch, the outer two change the pots for both pickups, from the ones wired in series to the ones wired in parallel.

Up on the switch is series, down is parallel.

Things to check for are:
1: The phase between the pickups;
2: The exact wiring of the pots for series;
3: What value should the series pots be, anyway?

Edited August 15, 2008 by Cernael