/diy/ - Do It Yourself

>>1000509
You can do it passively (a pair of resistors, or a potentiometer if you want a variable mix ratio) provided that the output impedances of the pedals are much lower than the input impedance of whatever you're driving (which is probably the case).

The resistor values should be significantly smaller than the input impedance (to avoid attenuation), and significantly larger than the output impedances (so that the total resistance of each leg is dictated by the resistance and largely independent of the pedal's output impedance).

If you can't satisfy that constraint, then you need to add a buffer amplifier to provide the desired high input impedance.

Given the schematic in pic related, you have
C=(G1*A+G2*B)/(G1+G2+G3)
where G1=1/R1 etc.

If G3=0 (i.e. infinite input impedance), then C=(G1*A+G2*B)/(G1+G2), i.e. C is a mix of A and B in the ratio of their conductances. If G1=G2=G, then C=(A+B)/2.