Hot Wiring Your Guitar
Continuing with the taps, firstly this month, I shall assume that you feel you have a beautiful guitar and that sticking nasty little switches in it will spoil it. Fear not, you can still extend the tonal range by using the existing tone control(s) to operate an earth type tap or an 'alternative hot' tap.
You can use any one tone control to tap any one pick-up. You cannot, however, use one tone control to tap two pick-ups, as the tap wiring will mix one coil from say pick-up 1 with the normal mix of coils from pick-up 2 when operated solo; so you won't be able to get a solo humbucker sound unless you replace the tone pot with a tandem pots unit and operate them separately on the one shaft. That's for another time though.
To operate a complete earth-type tap on one pick-up, the tone control and tap wire must be wired as shown in Figure 1, which assumes that the pick-up and control system is one of a pair on something laid out like a Les Paul. From 0-9 on the tone control (which will still function as a normal tone control as well) the pick-up will give the normal series coils humbucker sound, but from 9-10, coil 2 will be earthed out via the tap wire, giving a single coil sound from coil 1, whose earth reference is also provided by the tap wire.
Figure 2 shows the necessary wiring modifications to operate a partial tap in the same manner, here the tone control uses the same capacitor for partial tap and normal tone operation. The effect is the same as the partial taps explained last month. The 9-10 on the tone control will take out the treble frequencies from coil 2, allowing the treble from coil 1 to dominate the sound, which will be thicker than that for a complete tap. In both partial and complete tap, there is no particular need to screen the tap wire, as at no point is it used as hot. However, Figure 3 shows a way of wiring a tone control tap where the tap wire becomes an alternative hot. Here, unless the guitar is already thoroughly screened, the tap wire should be screened to help minimise the extra noise that will come from dropping out the humbucking propensities of the pick-up when tapped. The diagram assumes the same guitar layout as before, but in this instance, from 0-9, the humbucker sound will come out and at 9-10, the signal will be taken from coil 2 via the tap wire and link wire 'a'. Coil 1 will not sound, and there is no useful partial tap to be had here.
This style of tapping leads me to another type of switchable tap that also selects signal either from the whole series coils system, or from halfway through. This method again requires good screening. Figure 4 shows how a SPDT switch will give either series or single (coil 2 operates, coil 1 is cut), and normally an on/on would be used immediately after the pick-up and before the controls. If you are completely rewiring a guitar, or maybe building from scratch, a point worth remembering is that if this type of tap is applied to both or all pickups, the use of an on/off/on SPDT switch cuts out the need for a pick-up selector switch, since each pick-up can be switched on, in either series or single mode, independently. Alternatively, an on/on DPDT switch could be used to tap both pick-ups simultaneously in a two-pick-up guitar, though I would suggest that this cuts some attractive mixing possibilities.
Generally speaking, deciding which coil you are going to cut out will have an important bearing on the tone. In the bridge position, using the coil furthest from the bridge as hot will give a warmer sound than using the one nearest the bridge. If you prefer the sound of the coil nearest the bridge, perhaps you should consider the use of parallel coils instead of a tap, the coil nearest the bridge will tend to dominate the sound anyway. You might also be better off with the hum-cancelling properties of parallel out-of-phase coils which a complete tap eliminates altogether, or a partial tap eliminates partially. The same also applies to the fingerboard pickup to a large extent. Personally, I must say that for a long time I have preferred the sound, both on solo pickups and mixes, of tapped humbuckers to parallel coils and, as far as the bridge is concerned, am quite happy with a partial tap via a .033uF capacitor cutting out top from the nearest coil to the bridge on a close-in sited pick-up. I have also found a reasonably convincing 'out-of-phase' Strat sound can be obtained from a partial tap operated on the rear coil (nearest bridge) of a pick-up sited further forward. I find the top edge that a tap gives sounds less constricted than parallel coils and it is possible to be much more specific about harmonic content. Variation in harmonic content can have a drastic effect (good and bad) in an out-of-phase mix of one sort or another though and for this reason, as well as the odd studio type situation, where hum becomes a problem sometimes, I believe firmly in retaining the option of parallel coils as a switchable facility but as a backup option rather than a primary option.
I leave you with a point Jeff Baxter raised recently: that different guitars can have different things to say to the player, and offer different musical possibilities. I agree, but also believe that the tonal possibilities in a guitar can be exploited so that it might have as much to say to you as half a dozen others, and without the problems of coping physically with a variety of scale lengths, neck shapes, fingerboard cambers and so on. Changing from one guitar to another for the sake of the sound can play hell with your technique when it is at full stretch, but turning a switch one way or another affects your concept of your music at that moment without changing anything for your hands.
Feature by Adrian Legg
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