The 833A is a 450 watt dissipation triode with a mu of 35 and full ratings to 30 MHz. RCA introduced the 833 in 1937 and it is still popular in audio applications. The first example is an RCA, the second an Amperex, the third is a General Electric and the fourth is a Sylvania and the fifth is a Taylor with a zirconium spot painted on the plate to improve dissipation. The sixth seems identical with the Taylor, but is marked JAN 833A, LEWIS ELECTRONICS. The seventh example was made by Marshall Electronics (ME-833A) and was made in England. The eighth example was made for National Electronics in China. The GU-48 G or ГУ-48 G is a similar tube made in Russia.
Length = 8.81" Diameter = 4.59"
Max voltage = 3300 (4000 with forced air cooling)
Max current = 500 ma
Fil voltage = 10
Fil current = 10 amps