The pentode tube used in this circuit has 1.5 V filament. The circuit is a voltage amplifier with the 1U5 tube.
This circuit was found in English documentation from the 90's. Transistors are general purpose types....
This instrumentation circuit is from the June 1986 issue of Radio Electronics magazine. Equivalent...
This is an interesting idea that we found in the May 1971 issue of Radio Electronics magazine. It can...