This is a simple tubed mixer from the 50's. The circuit does not include the power supply and has 3 inputs with independent controls. The tubes are double and the inputs are high impedance.
This circuit uses a 6-bit A / D converter from Philips, and has its output compatible with most...
This ouput push-pull stage using bipolar transistors was found in a publication of the year 1968....
Found in a Popular Electronics from the 90s, this digital probe uses common components....