This excellent tube preamplifier was found in Radio Electronics magazine from July 1958. The power supply was not included. The circuit has several inputs.
This circuit compares the voltages of the two inputs giving as output 0 or 1 according to the...
This circuit provides voltages and a 1 kHz signal for measurement bridges. The circuit is from...
This circuit for audio applications was found in an English magazine from the 80's. The circuit...