I owned a power-amp of Rotel for 5 years and I didn't have a pre-amp, I was changing the volume within my DVD player, it had a volume control ranging from -80 dB to 0 dB. And when it was at 0 dB, the volume was loud enough. Then I bought a pre-amp from Rotel a week ago, and now when I maximize the volume on the Pre, the amound of volume coming from the speakers is a lot louder than before (DVD player at 0 dB again). How does it happen? Does the Pre add more dB or what?