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, obtained from a 1965 magazine, can still be assembled using some modern equivalent...
We found this circuit on an Elektor from the 90s. The frequency is given by capacitor C1. The...
This powerful regulator, shown in the figure is for 5V (TTL) is suggested by Motorola and makes use...