This circuit was found in a 90s Radio Electronics. It is intended to amplify the sound channel of analog televisions of the time. The integrated circuit used is uncommon today.
This circuit can use 20 to 100 mA relays with a general-purpose transistor such as the BC538. The...
The tone control in the figure below can be implemented with almost any operational amplifier. The power...
This circuit was found in a 1967 General Electric documentation. The components are from that...