# Pickup switching modelling tools?

I like to experiment with the wiring of my guitar. Usually this involves:

1. Designing on paper.
2. Soldering it all together.
3. Redesigning when I discover a flaw.
4. Heating up the soldering iron again.

I'm wondering if there are any tools out there that would allow me to do some testing of the design before I get the soldering iron out?

Edit

To clarify: I'm interested in modelling my wiring design so that I know it will give me the pickup combinations I'm after - series, parallel, etc. I'm not trying to model the resulting electrical characteristics.

For example this diagram is intended to give regular and series pickup selection. Can I test it without soldering?

Well, if you know the inductance of the PUs (ideally, also their AC ESR due to eddy losses), the resistance of the potis and capacitance of the cable (and of any tone caps), you can quite reliably predict the total response as the linear filter resulting from these components, and that's not too hard to grasp using complex analysis – just apply Kirchhoff's laws with Ohm's to all the AC complex impedances. That response can then be simulated with any standard digital IIR equaliser using biquad filters. To estimate what difference a given change to the circuit would make, simulate both the original and modified circuits this way, but invert the response of the original.

So far, it's somewhat obvious.

What's not included in such a model is the influence of the positions of the PU(s), of phase effects between them and so on, and that's perhaps the most interesting aspect. In principle, this is also easy to model with comb filters (there's also some nonlinearity in the string-pickup interaction but that isn't really affected by the circuitry).
Unfortunately, these effects influence every string in a different manner, so it's not really possible to simulate the changes from just the mixed guitar output. It is only really possible with signals from a hexaphonic pickup.

These calculations are of course exactly what processors like the Roland VG series (now merged with the GR series) do, as well as modelling guitars like the Line6 Variax models (though these, judging by the bad transient response, appear to actually use a FIR/convolution approach rather than physical modelling). Problem is, AFAIK none of these allow actually customising the simulated circuitry.

Take a piece of paper and a pen. Copy that diagram with all different switch settings. For each switch setting, draw the things the switch connects connected.

Then either carefully trace the electrical connections for serial, parallel, etc. (if you can follow the schematic that far), or do redraw the schematic by moving the things without disconnecting or connecting them, so that in each step of redrawing the schematic it becomes more simple.

Repeat that redrawing process until you see either serial or parallel connections of pickups (or something you recognize as definitely not being what you want).

• Yep, that's what I do currently - it's somewhat prone to human error :) Commented Sep 24, 2017 at 21:08