This circuit is from a 90s Popular Electronics. It consists of a power source for bass amplifiers of common types at the time that used symmetrical power and separating filters.
This linear oscillator was found in a 1968 publication. The operational amplifier is from that...
This circuit was found in Radio Electronics from May 1965. The SCRs and transistors are from that...
This Wien bridge circuit, using a 741 operational amplifier, was suggested by Texas Instruments in its 1996...