This elaborate mixer is from an Electronics Today International from the 80s. Operational amplifiers are common and resistors with no value determine the gain of the amplification steps.
This circuit controls a heating element with voltage from 6 to 30 V and current up to 3 A from...
We found this Vox in a 1969 Motorola documentation. Transistors support modern equivalents and the SCR can...
Found in a 90s Elektor, this mixer makes use of integrated circuits of the time. The supply must be...