This small tube amplifier appeared in Radio Electronics magazine in February 1958. The circuit is powered by the mains with a power transformer and output with different impedances.
Found in American documentation, this circuit is more sensitive than the previous one, as it uses...
This amplifier with differential input uses two old op amps but can be implemented with modern op amps....
We found this circuit in the Linear Applications Handbook of the National Semiconductor of 1994....