"TonyL"

Here's a problem that is causing me some grief. I'm rusty with electronics
these days, perhaps the experts in here can give me some pointers ?

I want to combine the audio outputs of an unspecified number of op-amps,
say 2-20. A simple mixer would do the trick...except I need the resulting
summed audio level to be constant as outputs are connected to and
disconnected from the system.


** I take it you want a mixer whose gain is a function of the number of
inputs actually connected.

So forget using the "virtual earth" summing method.

Feed each input to a high impedance summing point via a suitable resistor
( like 10k ohms) and the job is done.

As each new source is connected, the gain will drop in proportion to the
number.


..... Phil