re passive mixer shaffer wendy yale edu wendy shaffer writes i m trying to build a mixer for a friend of mine to run several things into a single boom box i have a circuit that uses an op amp powered by either a couple of v batteries or using some kind of power supply but in a catalog i was looking at recently a passive mixer for guitar was advertised taht doesn t appear to use any power at all does anyone know what the circuit for this would be because then i could just adapt it for rca jacks and save my friend and i alot of messing with batteries and plugs thanks well the fastest crudest mixer aside from just physically connecting all your inputs together directly is to run each signal through a resistor to a common output the resistors give some isolation so the signal sources aren t driving directly into each other taking a wild seat of the pants guess i d say that if you are mixing high impedance sources like some dynamic mikes electric guitar pickups etc your resistors ought to be maybe k k or so if you are mixing line level stuff or the outputs of a walkman or such i d go with k input output input input paul marxhausen university of nebraska lincoln grace happens
