A vintage electron tube amplifier with noise figure of 0.3 from Altec

At your risk. Any voltage or current can be dangerous. All safety precautions should be followed.


It is Altec 458A, 459A? plug in program amplifier. Noise figure of 0.32 is claimed for the Altec 458A [Noble].


What is the difference between the 2 amplifiers?


References:


High quality high reliability amplifiers for speech input systems - James J. Noble - Journal of Audio Engineering Society - April 1961, Volume 9, Number 2


459A plug in program amplifier  - operating instructions, schematic - Altec