Pre-amplifier of low frequency `` UP-6 ''.
Amplifying and broadcasting equipmentThe preliminary low frequency amplifier "UP-6" has been produced since 1933; it has been produced by plant No. 2 NUPP NKPT. The amplifier "UP-6" is a modernization of the previous amplifiers of the type "UP-3" and "UP-3N", but without the final stages. The amplifier is assembled on 3 radio tubes and is designed for preliminary amplification of signals from a receiver or microphone and for driving powerful terminal amplifiers of radio nodes.