I'm excited to be installing an Iron Gear Rolling Mill HB pickup in the bridge of my USA Strat.
Neck and middle are Fender Hot Noiseless and the Iron Gear HB will replace the bridge pup that I find too spiky.
For the bridge HB, I've decided on using the no-load pot as a gradual coil split so I can try and find some in-between sounds as will as a pure single coil. There will be a master vol, and a tone control for the two HNs. The bridge pup won't see a tone control.
My question is this - all the pots are 250k. Do I need to buy a 500k vol pot and do the special resistor thingy, or does the no-load (gradual coil split) pot not count as a load on the HB?
Comments
With a typical 250K log pot very little will happen from '10' until somewhere around '6' which is where the pot will get to the 40K - 50K region. If for example you like the sounds in the 2K - 5K region you may have trouble repeatedly dialling them in as you won't have enough resolution with a 250K pot (you've effectively wasted the range between '10' and '6'). A 50K or 100K log pot is actually a better choice than 250K, and the steeper the log curve the better (ideally something like a 5% taper if you can find one, but the typical 10% taper of a modern CTS pot isn't bad). If you want the reassurance that your humbucker is categorically fully humbucking at '10', you can convert a regular pot to no-load yourself (loads of videos online, but briefly it involves cutting the resistance track). In the case of a spin-a-split the no-load aspect ensures the connection between the coil junction and earth is completely broken when the pot is at '10'. Also, you may find you don't use sounds below a certain resistance (for arguments sake, you may find the split sounds below 1.5K too thin). In this case you could wire a 1.5K fixed resistor in series with the pot such that the lowest setting of the pot is always 1.5K and easy to find.
In your situation I'd definitely start with your existing 250K pot - it will work but with the aforementioned caveats. If you find you do really like the spin-a-split and you want more precise control then maybe try converting a 50K log pot (e.g. a Clapton volume pot) to no-load, or install a fixed resistor, or both.
It's been many years since I played with a spin-a-split. Ultimately I wanted a more conventional control setup, but playing with it helped me determine what values of fixed resistor worked best for me with partial coil splits. There is also the Peavey T60 rotary split and tone control circuit which seems like a good idea in principal, but is less useful in practice, and works best with a 'S' taper pot (you can substitute a linear pot, but some of the sounds will be bunched together).
http://www.thefretboard.co.uk/discussion/89942/caspercaster#latest
[img]https://i.imgur.com/eN9altO.jpg[/img]
On to the wiring - a few things to check/amend:
Firstly, the final lug of your volume pot needs to be connected to earth for that pot to function as a voltage divider, and it isn't connected in your drawing. And where is the earth connection for the output? Personally I usually solder the earth side of the output to the back of the volume pot, then the third lug of the volume pot, then on to the output jack - saves bending the third lug onto the back of the pot, which if not done with care can break the connection between the lug and the end of the track ( it's only a crimped connection).
Secondly, the spin-a-split does need to be connected to earth. Via the back of the tone control is fine assuming that is also earthed. The tone control pot 'should' be earthed via the aluminium foil or metal shield plate on the back of the pickguard, but there often isn't good continuity, so a soldered earth connection between the back of the volume and tone controls is good practice/ belt and braces. Check the earth continuity with a meter if you have one, or just add the extra earth whilst you correct the volume control wiring (you.could go from back of tone, to third lug of volume pot, to back if volume pot making a soldered connection at each of those three locations).
Did you convert the spin-a -split pot to no-load? If so, did you cut the trace at the correct end of the track?
Finally, just general checking of connections, are all soldered joints good etc, and are they actually as.drawn? Also, for your switch, are the commons in the locations as you have drawn them - I've seen the odd switch where the commons are at the other end of the switch - Stew-Mac used to sell a switch with the lugs transposed like that.
Hopefully you'll have it sorted.soon.
http://www.thefretboard.co.uk/discussion/89942/caspercaster#latest
http://www.thefretboard.co.uk/discussion/89942/caspercaster#latest