I assume you mean the analog audio (monitor) output and not the composite out, right?
There may be a software control for it, but from what I remember when I had my 6200 DAB I don't believe there is. Of course, this may be dependent on the software revision of the unit.
I know when I had one for my webstream I had to temporarily use the analog outputs to feed the streaming encoder until I received the digital input card. Since I couldn't find the control for the analog output so I ended up using a Henry Matchbox II until I switched to the digital output.