I just picked up a Yamaha M-70 amplifier rated @ 200wpc ('82 model). It has two large volume or "gain" knobs on the front for each channel. I recently ran the DVD player directed to it to play a PCM concert DVD (fleet. mac) and to listen to CD's. It really made a dramatic difference. I just set my knobs to a level I like and leave it alone. I thought I would miss the treb and bass controls but surprisingly it was not needed. Is this safe to do? Can I use the level controls on the amp as a volume knob and bypass the pre-amp? Thanks!!