Full - wave vacuum rectifier
The JJ 5U4GB is an excellent choice. This tube is for use in any 5U4 socket.
5U4GB is a directly heated full wave octal base rectifier for Hi-Fi and guitar amplifiers.
Base : OCTAL Uf = 5 V If = 3 A
Product information "6L6GC JJ Electronic"
JJ 6L6GC Pentode. The 6L6GC is the typcial output tube use by most US amercian amplifier models with output power exceeding 30W.
manufacturer: JJ Electronic