The 6L6G and 6L6GT have a maximum anode dissipation of 25 Watts and an upper limit for the anode voltage of 350 Volts. The 6L6GC is an uprated version designed for a maximum of 500 Volts on the anode and a dissipation of 30 Watts. This would be employed as a pair in Class AB1 push-pull for an output of 54 Watts.
For single ended Class A use the ratings are the same as the 6L6GT - 350 V and an output of around 11 Watts.
Electro Harmonix is an American reseller of Russian valves. The actual manufacturer is not specified. The rebranding marks the valve as a 6L6EH. An internet search indicated mixed views as to their reliability.
The construction employs the modern pressed glass foot rather than a pinch.
The substantial anode.
The control grid is surmounted by the usual heat sink fin.
Looking through the hole in the anode wall the two aligned grids can be seen. The wires are shaped to pass flat across the cathode.
The wide glass tube envelope is 34 mm in diameter and, excluding the IO base pins, is 94 mm tall.
Reference: Data-sheet. Type 6L6GC was first introduced in 1968. See also1968 adverts.
