Can anyone provide me any information on this tube amp? It has the following tubes: 2A3 (2), 6SN7 (2), 6SC7 (1), 5X4G (1), N7GT (1) The first knob from the left is an on/off switch, then the following 4-5 knobs are on potentiometers, perhaps this is an old multi-channel P.A.? Thanks!