The circuit shown can generate signals up to about 100 kHz and has the advantage of using an amplifier stage which isolates the load circuit from the oscillator, providing more stability. The circuit was obtained from a 1960s publication.
In this circuit the oscillator must be supplied with 150 V and, in addition, a voltage of 6.3 V for the filaments of the tubes.
The signal is sinusoidal and its frequency is determined by R and C whose values ??can be determined by the nomogram of figure 1.
Figure 1 - Nomogram to determine the values ??of the components.
In the example, we see that to generate a 100 Hz signal we need 30 k resistors and 20 000 pF or 20 nF capacitors.
The signal generated is sinusoidal of good quality. The oscillator circuit with a valve 12AX7 is shown in figure 2.
Figure 2 - Oscillator complete circuit.
