With a 475 V supply, this amplifier published in Radio Electronics magazine in January 1958 offered good power. The amplifier used 4 tubes.
This circuit was obtained in a Electronics World of 1968. The transistors can be equivalent as the BC558...
This basic tone control circuit employs a Philips NE5538 operational amplifier, but can be adapted to work...
Using JFETs, this circuit from a 90’s American documentation can generate signals of 0.15 Hz. The...