This mixer with 20 dB gain per channel uses RCA's CA3048 integrated circuits. We found it in the July 1971 Radio Electronics magazine. The power supply does not need to be symmetrical.
This circuit is from old European documentation. R1 depends on the output voltage of the...
This SCR circuit activates a buzzer when triggered. The circuit is from a Popular Electronics from...
This 130 V drive uses an integrated circuit not very easy to find, which is the LM143. The circuit is...