Post by JohnH on Aug 1, 2019 21:10:35 GMT -5
Two Twin-coil Pickups
Optimise your switching
These notes show a range of ideas for wiring a guitar with the classic SG or LP arrangement of two twin-coil pickups.
Choosing the best switching is a matter of taste, as to whether to have just a few tones with very simple switching, or to have ultimate versatility, but with more switches to control. Whatever choice is made, there are a few principles, which I believe are important:
- The connections between coils should optimise the hum-cancelling possibilities for the switching arrangement. This requires careful consideration of coil phasing.
- The switch operation should be simple and intuitive
- Avoid ‘bad’ combinations, such as those with unnecessary hum particularly where there is a similar hum-cancelling option possible
- Minimise sound redundancy — avoiding too many sounds that are very similar
- Minimise switching redundancy,, i.e.maximise the number of different sounds to the number of switch positions
- The switches should be configured so that each provides maximum tonal variation, but consistent with the points above, to get the best ‘bang for the buck’.
Sometimes, achieving this means adding extra poles to a switch. That is OK (it is only a few wires), provided the operation of the switch is simple, and the resulting switch can be obtained.
The following steps through some possible options, starting with a single switch, and then adding more controls. In most of these, volume and tone controls are not shown; these can be put after the output from the switching. I’ve done this to simplify the diagrams, and because I do not find them very useful. I’d rather select the tones by switches since it is more repeatable. However, it is simple to add master volume/tone controls, or separate ones for each pickup as desired.
One Switch
Here is the basic humbucker switching. There’s not much choice here; one simple switch to select either pickup or both. Everything is in-phase and hum cancelling. Note I’ve shown the reversed coil in a different position on each pickup. This doesn’t affect this basic switching but is important when considering switching for other options like single-coil.
The ‘+’ indicates the phase direction of the sound. Red (north coils)indicates reverse wound and reverse polarity with respect to blue (south coils).
Two switches — Coil cut
One of the most popular switching options is coil-cut to give single coil sounds. To let the resultant combination of single coils be hum-cancelling when used together, make sure one of the coils which is active is reverse wound.
Other options for two switches would include series/parallel (needs a 4PDT switch to apply to both pickups)
Three switches — out-of-phase with coil cut
To get an additional out-of phase sound with two single coils, it is best to arrange for both active coils to be wound the same way, i.e. on one of the pickups, the ‘other’ coil is cut (different to the in-phase option above), so that it makes a hum-cancelling out-of phase option instead of a hum -adding one. Making this work, in addition to an in-phase option is a puzzle, but here is one version. This circuit reverses the phase of the whole bridge pickup, as a way of changing the coil which is the one to be cut.
Actually it is a pretty cool little circuit, since it gives you series connected neck or bridge pickups, separately or together, in phase or out-of-phase, or single coils separately or together, in or out of phase. Also, you can select either of the bridge coils separately (they sound slightly different). Apart from the single coil only options, all the combinations are hum cancelling. It can be done with two DPDT switches.
Pickup phasing with coil cut
This circuit is based on DPDT switches, with a centre ‘on’ position. It is deceptively simple, but with a huge range of sounds. The DPDT switches change each pickup from normal in-phase, to out-of-phase with itself. In the centre positions, all contacts are shorted, bypassing the lower coils resulting in a single coil sound. The out-of-phase sounds are hum adding if used singly, but used together are hum cancelling. Another surprising highlight of this circuit are the combinations of out-of-phase on one pickup used with single coil on the other. The sound is very close to single coil (plenty of high harmonics), but there is no hum. This is unusual, since most ways of reducing hum tend to cut the highs, as in standard Humbuckers. In all, there are 15 different sounds available.
Four DPDT switches plus pickup selector
This type of circuit is particularly intended for adding multiple switches to volume and tone potentiometers, in the form of push/pull controls. This allows switches to be incorporated, without affecting the guitars appearance. It is quite common to do this on guitars with four pots, which have separate volume and tone controls for each pickup. The most well known version of this is ‘Jimmy Page’ wiring for Les Paul guitars, which can be purchased as a signature edition from Gibson, and the schematic downloaded from their web site. The JP wiring provides four push/pull controls for coil cut, overall phase between pickups and series/parallel connection between pickups (e.g. allowing all four coils to be wired in series).
The following alternative version combines the coil-cut into one switch, and instead of overall series/parallel, adds options for parallel wiring of the bridge pickup coils, and the option of putting the neck coils out-of-phase with each other (as in ‘pickup phasing with coil-cut’, above). The diagram is as follows, including volume and tone controls.
The following is a table of sound settings for each switch combination:
Note:
- Sw2 and Sw4 override Sw1 for the relevant pickup
- On the diagram, all switches are shown in the ‘O’ position
- ‘-’ indicates that the switch does not affect this setting
