I just picked up a 1970s Ampeg B-110 120 w 8ohms and it has a "Hi Gain" input and "Lo Gain" input. What is the difference? I have noticed the lo gain is warmer and louder. Can I do damage to the speaker by playing my passive P bassin the lo gain input? There is also a three way switch at the top of the control panel that says "300 hz 800 hz 3000hz" What does this mean? There is also a two way switch next to that that says "Ultra Hi." I'm not sure what that means either. I cannot find much info about this amp online. I guess it was not very popular. It is pretty big for a combo amp. Thanks for any help!