What tubes does this use? What plate voltages?
The Warmenfat uses the 6GH8A tube. The beam tetrode type. This tube has a square window in the plate structure. These tubes are operated WAY below its maximum plate dissipation ratings and therefore should last over 10 years with daily use. The 6GH8A was one of the most common T.V. tube in the 1960's. They are great sounding, New old stock is abundant and they are economical too! (Although very difficult to design with. Wiring layout is critical.) BEWARE : The pin out for this tube is NOT compatible with the 12ax7 types.