This circuit is from a 1967 US publication. The valves used are 6AU6 which can still be obtained today from some specialized sources. The circuit can generate frequencies from 10 Hz to 50 kHz.

This circuit is from a 1967 US publication. The valves used are 6AU6 which can still be obtained today from some specialized sources. The circuit can generate frequencies from 10 Hz to 50 kHz.