yes, use ohm's law to calculate what voltage output you should get.
then adjust the gain to achieve that voltage.
adjusting the gain is what compensates for the signal input voltage, that is why it's there!
as long as you're getting the correct voltage output then your signal's input voltage is not the problem.
you could try using a tone recorded at a lower level, which will force you to increase the gain sensitivity, and therefore make musical bass louder, but will also increase your chance of clipping.