This percussion circuit was found in an Electronics World of 1968. The transistor may be general purpose and the power supplied at 12 V. The signal must be applied to an amplifier.
Using the name of varactor this circuit was found in the Radio Electronics magazine of July 1982....
We found this circuit in a 1960 Radioarama magazine. The instrument tests common general-purpose transistors...
This circuit uses an RCA module from the time. The circuit is from a Radio Electronics magazine from...