The "how and why" behind pot and resistor choice for a mix circuit?

[skiraly017]

I finally figured out how to add a mix pot to my Small Clone build but what I do not understand is how and why it works. The mix resistors are the 20k and 22k. I replacedthe 22k with a 50k pot and a 18k resistor is series. What's the math behind that combination?  I'm probably overlooking something obvious.

The reason for this question is because I'd like to add a mix pot to a phaser build. I've located the resistors that control the mix but need to figure out what pot/resisitor combination to replace one of them with.

Any insight would be greatly appreciated.

[DuncanM]

If I understand correctly, it seems that :

The 22k determines the level of the direct signal, the 20k determines the level of the effect signal.
You have replaced the 22k with 18k and a 50k pot so.......

18k with the pot at zero will give slightly more (1.7dB) direct level than stock and turning the pot up to max will give you (50+18) 68k causing the direct signal will be reduced by -9.8dB [22/68 expressed in decibels]
So by changing the direct level while the effect level remains the same you are able to vary the mix.....

A bigger pot would remove more direct signal and you'd have a vibrato option.......

[skiraly017]

So if I understand this correctly and the resistor I'm looking to replace in the phaser is a 150k, it's just a matter of finding a pot and resistor combination that offers more direct signal at zero and less direct signal at max?

[DuncanM]

I'd have to look at a schematic...... but essentially yes - something like a 120k resistor and a 1M pot. I'm not sure what it would sound like though...