What’s the relationship between gain (dB) and power (watts)?


Is there one?  My new used 300+ epic Bryston amp has a gain switch on the back toggling between 23 and 29 dB of gain.  
redwoodaudio
That gain switch is like a gas pedal. If the driver has a strong foot, then the pedal is set to 23 to take into account the heavier push to get full power. However, a driver with a weaker foot will set the gas pedal to 29, making it easier to push for full power. The engine does not know the difference nor cares.
Awesome question and one I’ve been contemplating myself.

and awesome answer MC, thanks to the op and the og