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Hot Wiring Your Guitar

Bypass Switching


Broadly speaking, most electric guitarists employ two distinct playing modes during a performance: a loud penetrating tone for melody playing and soloing, and a softer less obtrusive one for rhythm and accompaniment. I'm sure I'll get lots of indignant letters now, having suggested that most players are somehow limited, but the design of the hardware will bear me out.

Many guitar amplifiers, for example, have two sets of controls which can be switched between at will; on the guitar front (pun intended!) most Gibson guitars still have their pickup selectors labelled 'Rhythm' and 'Treble'. On these instruments it's evidently intended that the fingerboard pickup should have its controls set for the softer rhythm sound, while the bridge pickup is used for lead playing. As it happens, the fingerboard pickup tends to be the louder of the two because the string vibration is greater at this position, and in the days when I played a Les Paul copy I usually used the pickups the other way around; there's always one who has to be different, isn't there?

The Fender Jazzmaster and Jaguar guitars, currently enjoying a modest resurgence of popularity despite being discontinued, use a slightly different system. Two completely separate sets of tone and volume controls are fitted, and one or the other can be selected with a small switch.

In terms of today's rock guitar styles, the lead setting is often all-out maximum everything, and it's doubtful whether any controls at all (other than self control) are needed for this condition. In other words, a simpler arrangement could be to have a bypass switch which just cuts the controls out of circuit altogether. I first came across this idea when playing a Shergold Modulator guitar which had a bypass switch built into one of its interchangeable control modules. It was interesting to note that even when the volume and tone controls were set at maximum, operating the bypass switch still caused a noticeable increase in the volume and brilliance of the guitar. The mere presence of the controls connected across the pickup was loading its output and causing a loss of signal. As soon as I could, I tried the same thing on one of my own guitars, and although the loading effect wasn't so serious, I was pleased to have the ability to switch between full and reduced volume repeatably; no more fumbling with the volume control!

Figure 1. Plans of the proposed bypass.


A Bypass Scheme



You can build your own bypass very easily, as shown in Figure 1; often the simplest things are the most effective. If you have one volume and one tone control, you'll need a double pole double throw (DPDT) switch; choose one with a generous toggle if you can, because you'll want to be able to operate the switch unhesitatingly when you're in a hurry. If you have two volume and/or tone controls, or your guitar is stereo, Figure 1 should be duplicated; alternatively a four pole double throw switch will make bypassing more positive, since you won't have to remember which switch is which, or in some cases operate them both at once. 4PDT switches are usually only available in mini-toggle form, however, which makes them trickier to operate in a panic. The choice is yours.

Figure 2. Bypassing a Stratocaster.


Things are more complex when it comes to three pickup guitars. If yours has three volume controls, the virtual non-availability of suitable six pole switches means you're restricted to three separate bypass switches; a messy solution. Stratocasters are a special case, as always; it's a simple matter to cut out all the controls in one fell swoop with a single DPDT switch, and the arrangement is shown in Figure 2. The switch placing is up to you, but it should preferably be in that magical (non-existent?) position that's easy to reach and yet simultaneously difficult to knock accidentally.

The Photograph



The author's guitar — see 'The Photograph' below.

The picture shows my favourite lead guitar; I know that if I can't play it on this, I won't be able to play it on anything! Originally a Gibson L6S Deluxe, the guitar has had new Schaller machine heads, a plain ebony fingerboard, new pickups and wiring, a stainless steel scratchplate, a new bridge and tailpiece, and it's been refinished. In a nutshell, there's not much of the original instrument left!

The wiring is a kind of sampler of the techniques covered in 'Hot Wiring Your Guitar' articles since E&MM began. I used DiMarzio Dual Sound pickups with four conductor cables, and the circuitry includes: bypass capacitors on the volume control (April 81), phase reversal (July 81), three way switching on each pickup (October 81), stereo (May 82), an ARP hexaphonic pickup (July 82) and a bypass switch.

I have found the conventional passive sort of tone controls pretty useless on a guitar of this sort, especially with all that switchery available; I didn't want to use active circuitry, so there is just one knob, a dual ganged volume control. The jack socket is fitted to a Stratocaster style recess plate, to stop the plug sticking up in the way, and because I like them. The ARP pickup has its own socket, which feeds a home built six channel fuzz unit; sometime this century I may get round to building a full scale guitar synth, but don't hold me to it!

Incidentally, if you were wondering why the wiper of volume control 2 and stereo output 2 in Figure 1 of May's Hot Wiring were connected to earth, puzzle no more; the wiper should go direct to output 2, and neither is earthed.



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Synclavier II

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Discotek


Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.

 

Electronics & Music Maker - Feb 1983

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Feature by Peter Maydew

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