A forum member asked about a custom GR-1SF layout based on the balance pot & tone switch diagram, but with the added option of coil splits on the pickups. The stock hole layout was to be maintained, so push/pulls are the easiest solution. One push/pull would allow both pickups to be split at the same time, and two push/pulls would allow them to be split individually. However, in each case it would be splitting to a fixed coil. By inter-linking two push/pulls you lose the option of individual splits but gain the ability to split to either coil and have the humbuckers as series coils (standard) or parallel coils.
As Tonerider pickups are being considered for the build I've used Tonerider colours in the diagram. They use red (hot) and black for the slug/north coil, white and green (ground) for the screw/south coil and have a bare shield wire (if using another brand of pickups you'll need to determine which colour pairs they use for each coil etc.). The coils are ordered as the screw coil first (with the ground connection) which links to the slug coil second which has the hot/output. A standard split on Tonerider humbuckers would give you a pair of slug/north coils when the pickup selector is in the middle position, which isn't hum-cancelling. So, on the diagram I've re-ordered the neck pickup's coils so that when split and in the middle position you always have a hum-cancelling slug/screw pair, either slug bridge and screw neck or screw bridge and slug neck. The trade off is you can get either coil on each pickup, but never the same coil on both pickups at once. Given the lack of shielding in a hollow body and the potential for noise, I think hum-cancelling splits are the better choice.
The diagram isn't as complicated as it looks:
The push/pull options are as follows:
MV = Master Volume, MT = Master Tone, up = Push/Pull up, down = Push/Pull down
(Setting affects both pickups)
You will typically want the bridge pickup split to its slug coil, so I've configured the layout so the default split when you pull the Master Volume up is bridge slug coil and neck screw coil.
In the diagram, the left side lugs on the push/pull switches are the bridge pickup's connections, and the right side lugs are the neck pickup's. If you look at the Master Tone's push/pull lugs, the left side has the bridge pup's red at the top (slug hot) and white in the middle (screw hot) which is the standard order for the coils, green then goes to ground and black to the Master Volume push/pull. The right side of the Master Tone's push/pull has the neck pup's white at the top (screw hot) and red in the middle (slug hot) which is the swapped coil order, the black then goes to ground and the green to the Master Volume push/pull. Basically, this connects the bridge pup as screw->slug order and the neck pup and slug->screw order, which allows the hum-cancelling splits.
The tone switch trims off the highs depending on the cap values, but it is a bit of an all or nothing item. In the first position you get your normal tone control, but in the other two positions the tone pot is disconnected and you just have the treble cut caps. If you have caps that match your sound and the tones you want and/or that suit the guitar and pups etc, great. However, if the caps don't suit, it'll never get used and is just a waste. The 0.0033 and 0.01 caps listed on the diagram are just a starting point, as they're similar to the original tone switch values... but definitely experiment before committing. I'd probably also try an 0.0022uF and 0.0068uF pair or similar values, given the likely warmth of the large hollow body.
The layout above shows what to connect to where, but not how you should make those connections. Given the difficulty in wiring or, worse, re-wiring a hollow body I would probably use 4 core shielded audio cable to wire this layout. Run single core shielded cable from the output jack to the master volume, and another length of shielded single core from the master volume to the pickup selector toggle. That gives you your 'hot' from the jack to the volume out and from the volume in to the toggle switch and the shield can carry the jack's ground to the volume and on to the toggle switch. Then, use the shielded 4 core to run between the volume and tone push/pulls. The cores carry the yellow and pink switch links and the green and black pickup wires, and the shield links the ground from the volume to the tone. I'd also use the 4 core shielded to run from the tone and balance pots to the pickup selector and tone switch, with 3 of the cores carrying the orange tone connection to the tone switch and the light blue and purple outs from the balance pot to the selector switch. Then run a ground link from the tone to the balance etc.
To make it even easier I'd probably use some Veroboard or similar as a pickup link so I could connect two lengths of the 4 core shielded cable to the loom as if they were the pickup leads, and then connect the pickup leads to the Veroboard (see below). The board could be insulated and then double-sided taped or cable tied to the underside of the pickup. Then, if you ever needed to, you could swap the pickups without having to remove the loom. As an added bonus, you could even swap the coil order via the Veroboard, rather than in the actual loom, and wire the right side lugs of the push/pulls the same as the left side lugs above. On the Veroboard you would just connect neck pickup red to loom lead white etc, and the coil order is swapped. Like so:
The image on the left links the pickups directly to the loom leads and matches my wiring diagram where the neck pup's coil order is swapped in the loom. The right image is where you wire the loom symmetrically with both pickup's connections the same and swap the neck's coil order by cross-connecting the pup leads on the Veroboard instead (not confusing at all). You could even put the tone switch caps on the Veroboard for easy access, and just run wire links from there to the tone switch.
Anyway, enough prattling, it's another option for the GR-1SF. Questions, comments or derision at your convenience.
Reply With Quote