Filament source (T398E)

Despite being transistorized, this is a constant current source circuit for 1 V valve filaments such as the 1H4 tube.

High Stability 10V Regulator (CB1582E )
Hig stability is the main feature of the 10 V regulator circuit shown in the figure and suggested by...
Three-phase motor control (CB7268E)
Suggested by Sprague in the 1980s documentation, this circuit can control three-phase AC motors....
Bass and Treble Control Preamplifier (CB16800E)
This circuit uses a 709 operational amplifier that is no longer common today. However, the same...