J3RK
22
The gain controls the input level, and the volume controls the output of the channel to the main mix. The function does overlap a bit, but they are different functions. I haven’t gone into the BB docs in depth, and just use it the way I would any other mixer.
In a general analog (simplified) circuit though, the gain is a ratio set by (typically) an op amp circuit, and is the ratio of two resistors (or pots / pot and resistor) that controls the level at the output of the circuit. This is actual amplification. (and can result in overdriving/distortion/etc.)
The volume would then be a divider circuit AFTER this, which is typically an attenuator (just reduces from the maximum level).
This is a pretty big simplification. There are lots of articles on this out there.
Since the Bluebox is digital, I’m guessing that the signals are controlled digitally until they’re output via the final DACs. So similar theory, but different implementation. I don’t know as much about the digital aspects, or how much analog circuitry is inside the BB. I had it apart once to replace the screen, but I can’t remember what’s inside. 
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