Low frequency amplifier "UP-3".
Amplifying and broadcasting equipmentThe low-frequency amplifier "UP-3" from the beginning of 1929 to December 1930 produced plant No. 2 NUPP NKPT (formerly "Profradio"). The amplifier is designed for radio broadcasting stationary nodes. The amplifier has 3 pre-amplification stages and a push-pull output stage with 6 tubes, 3 in each arm. Since December 1930, the plant has been producing the upgraded UP-3N amplifier.