I am preparing to fire up an ultrasonic welder (sonopet 1000) It is a 70's vintage valve unit with 6JS6C valves for output in what looks like a class B setup with transformer drive to the grids The real weird thing is that it uses a quasi complimentary topology with 15 valves in parallel per side. PSU has +/- 700V rails and separate heater supplies tied to the cathode, one to -700V and the other to the anode of the other bank of valves who's anodes are tied to +700V, load is fed from the centre. I always liked this topology but never thought anybody would use it with valves, I thought the output stage was class C with a tank circuit initially. Rated output is 1 KW. All valves look good heaters work but it is currently smoking bias resistors, I have no load connected yet so I will arrange a load and replace all the small electrolytics before firing it up again.
Does anybody know of any valve amplifiers using this arrangement? It would seem like an excellent way to drive electrostatic speakers if the voltage was higher. Does anybody have a schematic of such a topology, mostly the bias and the drive is of interest.
Does anybody know of any valve amplifiers using this arrangement? It would seem like an excellent way to drive electrostatic speakers if the voltage was higher. Does anybody have a schematic of such a topology, mostly the bias and the drive is of interest.