One thing I thought I would mention is that people with digital speakers often can only adjust volume with the rotary volume knob on the digital speakers......that is "setting volume level" in the mixer SOMETIMES won't affect the output volume. Just another thing which makes this a hard task. I used to be an audio-visual equipment technician, and I'm sure there is a method for making an "automatic volume level" control circuit; but it would be tricky and you would need 2 different circuits...one for digital data and 1 for analog.