[uwood]

Hello, I try to understand the gain stages of the 4 channel mixer of the field kit. 

Do I get it right, that U1 hast fixed gain of 1 (non-inverting buffer) and U2 has a fixed gain of 10 and U3 gain of 20?

The 100k RV-Gain pot only works as a voltage divider for the buffered input signal?

The input gain control with the pot does not work for one of my audio sources. Pot is to sensitive, I can only adjust from to quiet to already clipping. 

Can I get a "finer" gain control and less gain when I reduce the 1M resistor on U2 to 500k?

Thanks!

Schematics Link

[Jackieflipflop]

Hello uwood.

Correct,
U1 is a buffer, U2 is a inverting configuration with 10x gain. U3 has a non-inverting gain of 21 that can blend between the high filtered and the low filtered signal.
RV1 works as a voltage divider/attenuator for the incoming signal.
Surely you will half the maximum gain if you replace the 1M with a 500k but here a question:
"The input gain control with the pot does not work for one of my audio sources" means that the pot is damaged?
In that why not replacing the potentiometer instead?
Or maybe i missed something

[uwood]

Maby my english is to bad. The range of the pot is not right for the device. Pot is to sensitive, I can only adjust from to quiet to already clipping.

Anyway, I've reduced the gain of one channel and replaced the opamps with burr brown opamps and now the pot range is right and no clipping and cleaner sound.