By Ed Malaker
Posted 03/28/2025
Question:
Hi!
I’ve been reading your guides on coil-splitting and was wondering about a calculation. A 7k resistor with a coil-split would result in a 20% of the second coil. What is the calculation that I can use to get the exact values? I thought X/(X+Y) = Z would get me the resistor value. With X being the resistor, Y the coil value / 2 and Z the coil split value. This, however, does not give me the right values. I would love to have the formula, so I can calculate before soldering!
Sem
Answer:
Hello Sem, and thank you for the great question. Unfortunately, I regret to say I do not know of the calculation you are asking or how you can find it. Though electricity is still free to pass through the second coil when the coil-split is engaged, electricity is much like water and prefers the path of least resistance. I would be surprised to learn that 20% still passes through. If you have read or heard that, I cannot argue and find it interesting, but I cannot tell you how they arrived at that value.
However, one thing I do know is that you can force more of your signal to pass through the second coil using a resistor. Check out our article about adding a resistor to the coil-split here: Lindy Fralin Partial Tap Resistor. You can modify this even more by switching out the resistor for a small variable resistor for ultimate control over how much signal passes through the coil without requiring an exact value. Details on this can be found here: Partial Tap Resistor – Advanced Techniques.
Sorry, I can’t be of more help. If you do learn about such a calculation, please share it with me as I’m quite interested.
Thanks for reading Humbucker Soup!
Ed Malaker