[sdiy] OT - DIY mixer

[Ingo Debus]

harrybissell wrote:
> 
> This can be tricky. The summing amps have to be able to source / sink
> enough
> current to handle all channels. This gets worse as channels are added.

I don't understand. If it's just a standard inverting summer with a 
gain of 1 from each input to output, why is current an issue?

However, noise performance gets worse with more inputs. Noise gain is 
the sum of the gains from all inputs plus 1.

Ingo