This fader or fader was found in a 90s Popular Electronics. The circuit uses transistors that are equivalent to BC548. Input and output cables must be shielded.
This 1965 General Electric circuit uses a "Thyrector" that is a suppressor of the time. The...
We found this circuit in documentation from the 1970s; The circuit uses Japanese transistors of...
The output voltage depends on the zener diode. Zener in the range between 1.2 to 12 V rated to 1 W...