This circuit is from an old Japanese publication of 1962. The circuit uses two batteries, one for the filaments of the tubes and the other one of high voltage for the plate circuits.
This circuit makes the RIAA equalization for signals obtained from a turntable for signal recovery in other...
This circuit also detects IR, providing LED indication. The circuit is used to indicate humidity in...
The circuit shown is a suggestion by National Semiconductor in its 1994 Linear Applications...