Sigma 500 Rev B has been released! What is the difference? A 3rd mode has been added called Passive Mode which allows you to use any rack mount or table top preamps!
In passive mode, the summing circuitry gets isolated from the rest of the electronics. The output of the summing portion gets connected straight to the output XLR jacks. That way if you wanted to use any preamp you own, not just the 500 series compatible preamps, as the summing amps you can.
How do you get to passive mode? You just turn the unit off! The circuitry makes all the required connections and the Sigma 500 is no longer using power.
Check out the website for more info: www.recordingwithgas.com