This circuit is from a manual from the 80's and the operational one used, uncommon nowadays, can be replaced by a modern equivalent. The power supply must be symmetrical.
This amplifier was published in the July 1961 Radio Electronics magazine. It announced the release of...
This circuit was found in a 1967 Electronics World. SCRs are according the controller load,...
This sophisticated circuit using a liquid crystal display was found in Radio Electronics from the...