3-channel preamp (T484E)

This 4-tube circuit was found in an American publication from 1947. It is intended for audio distribution lines using a transformer source.

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1 W amplifier with the LM390 (CB13753E)
This circuit is from the National Semiconductor Audio Handbook. The amplifier operates with 6 V...
Wiretapping Amplifier (CB19339E)
This is an amplifier that uses a pickup coil placed next to the telephone set and the listening is done in...
3 to10 MHz Oscillator (CB13020E)
The modified Hartley oscillator seen in the figure can generate signals ranging from 3 MHz to 10...