DGT coil split resistor question

[JoJo]

As mentioned some time ago in another DGT-related thread, I did some extensive rework on my DGTs electronics compartment: new pickups, three 500KOhm Push/Pull pots (individual coil splits on the two volumes and an out-of-phase switch on the tone pot).
However, I am not quite sure about the actual wiring of the PRS coil tap, so my experience cannot be transferred directly as I am now using splittable Bare Knuckle Abraxas pickups instead of the stock pups.

To conclude: I used a 100kOhm resistor on the neck coil split and a 200kOhm resistor on the bridge PU split. Initially, I did some trials with an additional cap ranging from 47 to 220p in parallel to the resistor. Finally, I just stuck with the resistor: the caps weren't as dominantly changing the sound and I got the best results (at least to my ears) without using one...

Finally, I would still go with Johan Allard's recommendation: just try different resistor values, if that doesn't the trick, try a cap from 47pF to 1nF switched in parallel to the resistor.

Good luck!

 

[mildew]

I used a 2.2k resister on my 59/09 bridge tap to add a bit more guts. in series with the tap to ground.

 

[Johan Allard]

I think what you're talking about Jojo is a treble bleed circuit. Not a coil split?

Thinking about these values some more again today. I think I've worked out the formula. Consider this simplified diagram:

Two values for X are simple. If we disconnect X (infinite resistance), both coil A and B are used and the overall value witll be 8.8K. If we ground X with no resistance, coil B will never be used and the overall value will be 4.4K.

But if we assume a 4.4K resistor at X, that means that it's as much resistance from coil B and from the resistor at X, which would mean that half of coil B would be used, or we'd get a total value of 6.6K.

If we use a 2.2K resistor, it's then twice as hard to draw current from the coil than from the resistor, which means that 2/3 will be from the resistor and 1/3 from the coil, 4.4K + 1.5K = 5.8K total value.

I believe that the correct calculation for total value would be:

X
------ x B + A = total resistance value.
X+B

X/(X+B) = how much of the current are being used from coil B. If we test:

- Zero resistance and we get 0 divided by 4.4 which is 0, and 0 x 4.4 is 0. I.e nothing is coming from coil B, exactly what we're expecting.
- infinite resistance and we get infinite divided by infinite + 4.4 = 1, and 1 x 4.4 = 4.4. All of coil B is used, exactly what we're expecting again.
- and a 2.2k resistor: 2.2/(2.2+4.4) = 1/3 is coming from coil B, again exactly what we're expecting.
- and the final example would be a 1.1k resistor (which is the other recommended value from the PRS diagrams): 1.1/(1.1+4.4) = 1/5 or 0.9K is used from coil B for a total value of 5.3K.

What do you think? Make sense?

Obviously there's more to pickups output than strictly their resistance value such as magnet type and wire used. But if you want to get scientific, you could still use this formula to work out how much of the other coil you want to use when splitting.

 

[JoJo]

I did mean a coil split, however with a different wiring, which I got from the German site guitar-letters.de (I originally meant to go with the "true split" mentioned there).
After some trials I ended up with the standard split, but with higher resistances, as no other resistors were available at that time.

This thread has stirred my curiosity, however. So I just ordered a bunch of resistors ranging from 1.1k to 91kOhm. Time to get the solder iron out and to have some fun again

I will report back as soon as I will have done some additional practical research to back up Johan's (in my eyes absolutely correct) theoretical explanations.

Make way, experimental physicist at work...

 

[Mike M]

UPDATE. I installed the PRS spec resistors on my Push/pull and it is a huge improvement. Split coil is louder, better sounding and very different than full humbucker. Very pleased!

 

[Boogie]

Now that's a happy ending. B)