This circuit is from an Electronics World of 1968. The transistors are of the time and the power is supplied with a voltage of 40 V. The circuit is high fidelity.
This basic configuration of an astable multivibrator was found in a publication of the year 1968....
This simple circuit was found in an English magazine that no longer exists, January 1970 issue. This...
The circuit shown uses the 741 operational amplifier, but lower noise and higher gain equivalents...