This 1.5W tube amplifier was found in an American documentation from 1947. It is a direct rectification circuit without the need for a power transformer.
We found this circuit in the October 1994 Electronics Now magazine. The CMOS IC is uncommon these...
This circuit eliminates hiss and other noise from audio sources by cutting frequencies above 10...
This circuit is from a 60's documentation. The capacitance C1 can be between 20 pF and 0.01 uF...