I am a newbie and I may be buying a used AI Contra model 310 BA. Where can I find information about this older model? It says 250 watts on the back and has 6 dials: volume, bass, mid, treble, brite, master volume. It has two pairs on inputs for jacks with a pair of high/low input and a pair of send/return effect loop. It sounds great, but I was curious about how to tweak the sound with the various controls and inputs. I am using a Fishman full circle pickup without a pre-amp (I plan to buy a pre-amp in the future) on my Englehardt ES-1. What would be a fair price for this model that is in good condition? Any info would be appreciated.