This circuit was found in a National Semiconductor manual from the 1980s. The integrated circuits used are equivalent. Note the need for a symmetrical power supply.
This circuit is from the National Semiconductor 1977 FET Databook. The FET can be BF245 or MPF102...
This 32 A circuit uses SCRs of the time. We found it in a 90s General Electric documentation. The...
This tone control was obtained in the Audio Handbook of the National Semiconductor of 1977. The...