Hot Wiring Your Guitar
The term 'stereo' when applied to guitar wiring is something of a misnomer. 'Two channel' would perhaps be a better name: the first point to be made when talking about stereo guitars is that they don't really give a stereo image as such, except in very rare cases. You might expect the sound of different strings to be heard from different places in the stereo image, but what in fact happens with the well-known 'stereo' instruments from Gibson and Rickenbacker — and the wiring described in this article — is that each pick-up is connected to its own independent output on the guitar. If that doesn't sound as exciting as you'd hoped at first, read on; as far as I know, stereo wiring has been around longer than coil-taps and phase switching, and can be very useful both on stage and in the studio.
In a live performance, the important feature is that you have two signal paths which can be on separately or together, selected by the guitar's pick-up switch. Thus, you can have a separate effects unit (or string of effects units) on each output, and switch between them from the guitar. You don't need to stand near the effects to switch them on and off — they can stay on all the time. You only have two combinations of pick-ups and effects to choose from, true, but that's one more than you had before, and it's often quite sufficient.
In the studio, or anywhere that a bit more flexibility is required, the ability to treat each pick-up completely separately is a great boon. Normal non-active guitar tone and volume controls interact with each other in various weird and wonderful ways, and although players usually get used to these peculiarities, there can be very few who actually like them. Try connecting a stereo graphic or parametric equaliser to a stereo guitar and see how many sounds you can get that you didn't think your instrument was capable of! Many guitar amplifiers have two input channels with separate volume and tone controls, and the same sort of effects can be had using these, although on a more basic level.
Another useful trick which works especially well for solo players is to have a separate volume pedal on each pick-up channel, allowing continuously variable tone control whilst playing — you'll probably need to sit down for this one! Finally, and contrary to what I said in the opening paragraph, routing each pick-up to opposite sides of a stereo mix can give interesting effects. This technique is useful for broadening out solo or sparsely-instrumented music.
By far the easiest guitars to convert are those with two volume and two tone controls, such as Gibson Les Pauls, SGs etc. and some copies (oops, what have I said?). It's important that the pick-up selector switch should be of the 'open' type with four contacts, like that shown in diagrammatic form in Figure 1. These have two pairs of 'leaves', which contact each other when the switch knob is in the central position, but one or other circuit is broken to switch off the appropriate unwanted pick-up in the 'rhythm' and 'treble' positions. Some Japanese guitars have an enclosed switch with three contacts, and these don't allow separation of the two pick-up circuits; it's an easy matter to replace these with an American style selector.
The first thing to do is to separate the two outputs on separate screened cables. Once you've got the guitar unscrewed to the point where you can see the major electrical components, start from the output jack and trace its wire back to the controls. It should go either to both volume controls, or to two tags on the selector switch if it's the four tag type. Disconnect something appropriate so that the output cable goes to only one volume control/switch tag.
Now connect the centre conductor of a fresh piece of screened cable to the tag you've just freed, and connect its screen to the same point as the screen of the original output wire. The circuit should now look something like Figure 1; there are many variations, however, so don't worry if the selector switch comes after the controls on your guitar, or if the volume controls are wired a different way round. The effect will be the same.
We now have to connect these wires to the outside world; the easiest way is to use the ring and tip connections of a standard stereo jack socket, but this limits you to using a stereo lead all the time. A SPDT mini-toggle may be wired as shown in Figure 2 to give the option of reverting to mono if required without having to use a special lead.
If you're building your own guitar, or you can make space for an extra jack socket (careful with that drill, Eugene!) the most flexible arrangement is that shown in Figure 3. This gives mono or stereo simply by using the appropriate socket, together with a third option best described as 'twin mono'. The three conductor jack is the neatest connector, as it only requires one (twin core and screen) lead, but these leads can be difficult to obtain; home made ones tend to be unreliable, especially where they split into two mono jacks at the amplifier end. The Figure 3 arrangement allows the use of two mono leads, one in each socket, to give exactly the same results. Note that the jack sockets used in this circuit are the type with break contacts fitted, not the normal guitar jack.
If you wish to convert a guitar which doesn't conform to the ideal outlined above, don't despair; a bit more work is needed, that's all, and a bit more common sense since I can't cover all the possibilities. You should aim to end up with a circuit similar to that in Figure 1, but in some cases that may be tricky. The biggest problems will arise with guitars which have less than four controls, and no space to add more. On such instruments, any controls which there are only one of should be replaced with ganged potentiometers of the same value, one section for each pick-up channel; the tone control capacitors should also be duplicated.
Another solution you may care to consider is to do away with the tone control(s) altogether, and just have two volume controls if there is only room for two pots on your guitar. I don't have tone controls on either of my lead guitars, and I don't miss them at all. I prefer to use coil-taps and such to get tonal variation, and all these techniques (described in previous issues of E&MM) will combine comfortably with stereo wiring.
Finally, if you've got a weird guitar and you can't work out how to make it stereo, write to me care of E&MM with a clear wiring diagram and a SAE and I'll do my best to help you. Just don't ask me how to convert a Stratocaster (or any three pick-up guitar) since I can't think of a sensible way of doing it without losing one of the pick-ups, or at best radically rewiring it.