What is audio impedance what to use to audio match between 2 circuits? Does a transformer can be used to match impedance? As I understand it a circuit (source) would be 600Ohms and the (load) circuit would be 1500 Ohms that is impedance mismatch. But what determines the 600Ohm in the first circuit? The last resistor in the circuit would be a 600Ohms resistor? And which one of those 2 circuits would be high impedance and which one would be low impedance?