This circuit uses an unusual sensor nowadays, but the configuration can be adapted to more modern types, as well as the operational amplifier. The circuit is from an 80's documentation.
The correct connection of speakers and tweeters in a speaker to obtain better sound quality,...
This circuit with germanium transistors was found in a Mullard manual from 1960. The components depend...
This circuit was found in a Popular Electronics from the 90s. The components admit equivalents and the...