This Public Address amplifier was found in a 1947 amplifier manual. The power supply uses two transformers with two rectifier tubes.
This circuit was obtained in a 1991 Electronics Handbook. The publication no longer exists, but...
We found this circuit in Ferranti's 1974 transistor manual. The components are from the period. Note...
This instrumentation amplifier was obtained from Popular Electronics in 1993. The operational...