"TonyL" wrote in message
...
David Looser wrote:

Simply the star point is connected to the inverting input of the
op-amp, the non-inverting input being at AC ground. A feedback
resistor connects the output of the op-amp to the star point.


Thanks for responding.

Yes, that was how I was doing it. However, when I added a second virtual
ground op-amp the audio was killed completely at the outputs of both of
the
virtual ground op-amps. Is there something I'm missing here ? Is it
possible
to connect two virtual grounds together at a star point ?

No it's not. Why on earth were you trying to do that?

Also, is the virtual ground idea going to eliminate the problem of level
changes as the fan-in/fan-out numbers change ?


The beauty of the virtual ground mixer is that it is insensitive to changes
in the number of inputs (what you are calling "fan-in"). If you are getting
level changes as you vary the number of inputs you are doing something wrong
somewhere. What sort of op-amp are you using?, and what value are the input
and feedback resistors?

David.