All the way up is Unity Gain. 12 O'clock is about 6 dB's down. Bob from Dangerous suggests to start around 12'Oclock and hit the outputs of Protools into the summing bus pretty hard, then adjust it a bit. If you have a compressor on the output of the summing box back into PT, this is a good place to use the gain knob. The box has tremendous amounts of headroom. I only use my summing box now. I have an apogee Symphony with 16 outs and I use 12 of them into the summing box. The stereo image is quite extraordinary.
