Hi.
You cana fair bit of the wiring separate from the body using a cardboard template, but the final connections between the pickups and the Series/Parallel/Split switches will need to be done with the pickup wires poking through the F-hole and the switches on top of the body.
This makes it difficult to make a harness that will keep the wiring all together using tape or cable ties. Without anything to hold the pickup wires up, gravity will take over and they will fall down and be seen through the F-hole. So I'd think about either running the pickup wires around the front of the F-hole or using the cardboard template propped on top of the guitar to wire basically as you've shown, but using cable ties or tape to keep the wires in a stiff bunch that runs around the outside of the F-hole.
It really will be much easier to run the bridge ground wire out into the control cavity and to the back of a pot than to try and connect it to the bridge pickup base plate. There should already be a hole between the post hole and the control cavity (though the factory sometimes miss these).
Unless you've already got the Switchcraft socket already, I'd suggest looking at using a Pure Tone output jack. These cost only slightly more than a Switchcraft but hold the jack much more firmly due to the extra contacts. On a semi where removing and fitting parts is harder than on a solid body, I'd always recommend fitting the most reliable parts you can. I came across them a few years ago and now use them all the time, and others here have done the same and really like them. I did a write-up on them here
https://www.buildyourownguitar.com.a...ad.php?t=10122
Tone pots are a personal choice. The 'standard' humbucker selection is 0.022uF compared to the single coil 'standard' of 0.047uF.
My own experiments with cap values indicate to me that with the tone knob full up, the value doesn't really matter as so little signal leaks through the tone pot resistance that you can't hear the difference. It's only when the tone pot is rolled down so that there's less resistance and more high frequency signal flows through the cap to ground that the differences become more apparent.
The tone capacitor forms part of a first-order high-pass RC (resistor in series with the signal, then a capacitor between the signal and ground) filter with a 6dB/octave roll off above the filter 'knee' frequency. The R(resistor) in this instance is the pickup coil's resistance. The bigger the capacitor value, the lower the filter 'knee' frequency and the more high frequencies are rolled off to ground by it.
The tone pot is used as a variable resistor (which doesn't form part of that RC circuit but is there simply to limit the signal flow down to the capacitor). With the tone on 10, you've got 500k or 250k (depending on pot selection) resistance in between it and the capacitor, meaning that most of the high frequency signal passes through to the output jack.
With a tone control, some HF will always pass down to ground. Take away the tone control and the sound will be brighter and slightly louder as a result (this is what 'no-load' tone pots do with a break in the resistance track in the 10 position). But my experience is that the resistance really needs to drop down to nearer 120k befor3 you really start to notice the tone roll off properly.
Which is where pot value and the taper selection comes in.
Audio taper gives a quicker response to turning down the tone control than a linear taper. As the tone pot is used as a variable resistor, a 500k pot will take more turning down to get the same tone roll-off than 250k pot e.g. with a linear pot, a 500k pot on 5 is the same as a 250k pot on 10, so you should be able to see how all the tone action bunches up to be within the very bottom end of the pot's movement with a 500k linear pot.
So these days I prefer to use 250k audio taper pots for tone, for both single coils and humbuckers. You'll lose a very small amount of top end using a 250k tone pot on a humbucker, but it is barely noticeable to me (YMMV). I normally fit 0.015uF caps, as I never want the full mud sound that a bigger cap value can give, which helps give a more controllable and useable tone roll off over 90% of the pot travel. You'll always get more of the tone roll off happening right at the bottom end of the pot's travel, but without a custom taper, there's not a lot you can do about that.
But apart from tone pot and capacitor values, you can always swap from the standard 500k volume pot choice for humbuckers to 250k, which will roll off some highs, move the pickup's resonant peak down a bit and generally make the pickup sound softer
The pickup's impedance, inductance and capacitance combine with the volume pot resistance and the amp's input impedance and the guitar cable capacitance to form a low pass filter with a resonant peak. Changing the volume pot resistance can make noticeable changes to the pickup tone. Even within the normal ±20% tolerance range of an average potentiometer's nominal resistance (±10% for the better pots), you can tune the guitar's sound by measuring from a selection and choosing a lower or higher value than nominal. People generally tend to prefer the pots on the higher side of the nominal value on humbuckers (around 520k) to get them sounding brighter with a touch more sparkle. You can of course chose a pot with a lower measured resistance value to lose that sparkle and edge.
None of these selections are permanent and you can always play around with changing pots and caps as time goes by, though the semi-hollow nature of the guitar does make it more of an effort to do so. You may want the guitar to sound quite standard at times, so using the tone control is probably the easiest thing to do here, though altering the volume pot's resistance has a slightly different effect as you are moving that resonant peak frequency too, not just the filter knee frequency, so boosting a slightly different range of frequencies as well as just rolling off high frequencies.
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Originally Posted by Simon Barden
