This 6W amplifier with 4 tubes was indicated in an American documentation from 1947 to operate with recorders. The circuit uses a source with a transformer.
The power of this converter is not the greatest, it can only supply small fluorescent lamps,...
This circuit is in the very datasheet of Texas Instruments that manufactures the component...
Found in a PE Hobbyst Handbook from 1991, this circuit uses a common photocell as a sensor. The...