This circuit filters low frequency noise from the turntable motor. We found it in a 1989 documentation. The font doesn't have to be symmetrical, but it should have excellent filtering.
This small amplifier with a low impedance microphone that can be used for hearing aid was found in a...
I found this circuit in a Popular Electronics from November 1999. The magazine is no longer...
This circuit is from a 1987 technical documentation. It consists of a battery charger and a system...