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FAQ: Output Impedance Specifications

The lower the output impedance the better.  Cable capacitance will have less loading effect on the signal and any noise pick-up will be lower.

When active electronics were still very expensive it was necessary to maximise signal transfer between stages by equalising output and input impedances and it is this historical reason that some people still say that input and output impedance should be the same.   These days it isn’t necessary and the lower the output impedance the better.  Usually one would expect the input impedance of the following stage to be at least ten times the output impedance of the driver, but here the higher the impedance the better as it will load the driver less, reducing power dissipation.

There is a limit to the amount of current the output stage can drive and the load impedance should never be less than 600Ohms in order not to demand excessive current, but above that all is good.