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 was found in an old publicatio n from the year 1958. The circuit controls an external load by...
The focused circuit was found in the National Semiconductor's Linear Applications Handbook of...
If there is an indispensable household appliance in our kitchen these days it is the microwave...