Just a regular Jcm 900 4100 with 6L6gc pwer tubes!! The sound of the amp wasn´t very good probably the worst amp Marshall made!! Most of the sound was from transistors!! The valves weren´t doing very much!
It´s a marshall based eq, like most amps do, with an extra knob for the range, just like a krank. The preamp section is based on nothing in particular. Just built it first with no highpass and no lowpass in any stage and went from there!!