This circuit makes use of a specific 80's component and was found in an American manual of the time. A matrix keyboard allows you to select one of several music programs.
The integrated circuit of this amplifier is not very common today. The output transistors can be...
This circuit is from a1970 documentation. R1 may have 10k and P1 47k. The transistors can be BC558...
This circuit is from a 1977 documentation. It is powered by the power supply of the circuit under...