Convert Amp Gain to sensitivity?

Gaara
Gaara Posts: 2,415
edited August 2007 in Electronics
How does one go about doing this?

For example if I had a amp that was 500wpc , has a gain of 25db , and input impedance of 105k what is the input sensitivity? If it matters the source would be 2v and be run through a passive preamp.

I thought there was a calculation to take the gain and power and convert to input sensitivity, but I am having a hell of a time finding it.

Thanks.

Jared