Found in older American documentation, this circuit can monitor 3 or more voltages determined by resistors. Components admit equivalents.
Originally created to feed the filaments of a 12AX7 as an audio preamplifier to eliminate the...
The BFO or Beat Frequency Oscillator is used to receive telegraphic signals or even modulated in...
This circuit is a variation of the previous one, containing a modulation input. The components are the same....