TonyL wrote:

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.

Absolutely constant ? You need a thing called a hard limiter on the mixer
output.


I know a virtual ground is the standard method to mix audio but there's
another wrinkle here. I also need to send the summed audio signal to an
unspecified number of outputs, between 2 and 20.

You need a distribution amplifier for that.

All readily available off the shelf for a price.

Graham