My 30 Watt class A is louder than my 100 Watt Class AB?

It’s the gain difference and input sensitivity difference of the two amps!

Thanks. I re read the answers, watched the video, and it’s a bit clearer now! 

Hiraga has a gain of 26db, input sensitivity TBD.

Adcom has a gain of 27db, and an input sensitivity of 1.25V

I’m going to contact the vendor for the Hiraga PC boards I bought, and see if I can find out the input sensitivity.

Amp settings vary with gain.  I recently use the same preamp into two different amps, one of whiich can use 3 tubes for different power levels,  with the following results for the same voume level.

ZMA  40 wpc  -40dB

Techtron 300b 6 wpc   -45dB

Techtron 2A3  2.8 wpc  -48 dB

Techtron 45   1.8 wpc   -50 dB

So the gain produces the same valume at a lower setting but if I were to turn it up on a night when I felt particularly sadistic toward my eardrums, they woulld run out in order of power from low to high.

I thought it was ironic that the lower the power the more gain.

Jerry

The voltage gain of amplifiers is a convention, but not a rule. I think most solid state amps have 23 or 26 dB of voltage gain, but there’s no rule that forces this number. Lower gain may be a good thing given that so many preamps have too much gain already.

Also, there's no correlation between amplifier power and voltage gain.  From 50 to 500 Watts, amps following the convention will be just as loud at the same input.