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

To further confuse the issue,

Changes in amp output, measured in dB volts are directly related to SPL dB.
That is, increase amp output by 3dB and the SPL will increase the same.  Like with amps though, speakers have physical limits which cannot be exceeded

This is where my technical ignorance seems significant.  Maybe I’d need a textbook to understand this:


Well, think about how much an amp can do.  Amps can't have infinite power, or output voltage, right?  They are limited devices.  Every one of them. What limits them?  Among many things, the voltage available to the output circuits. That is the absolute limit of output.

Your gain is 20x (28 dB) for instance.  OK, but your maximum voltage out is 10 Volts peak to peak.

1 volt pk-pk in x 20 = 20 Volts pk-pk. 

With this amp, 20 volts out is not possible.   You need a bigger amp.  What you'll get instead is a clipped signal that goes up to 10 and hangs there until the input voltage goes back down.

None. :) 

Amps tend to, by convention but not requirement, have around 28 dB of gain, regardless of their power rating. :)  This is about 20x input voltage.

That is, put in 0.1V peak to peak input signal and you should get 2V peak to peak on the output.

Of course, gain only works so long as you don't exceed the output limits, whose absolute limit in a linear amp is by the power supply rails.  So, if your rails are +- 20V, that's your peak output.  With 20x gain (around 28 dB) this means your maximum input voltage is 1v peak to peak before clipping.