This months tube is a dissimilar double triode, a kind of tube which was not presented in the Tube of the Month series yet. So it is about time since there are many interesting tubes of this species out there. Here is the 6GL7.
Another comparison between the two:
6GL7 manufactured by Lindal (Japan):
Now let's have a look at the internal construction. Removing the glass tube reveals more details.
Clearly visible the different plate size of the high mu section (left) and power section (right):
The high mu section from the side:
The getter ring attached to the plate of the power section:
The top mica disc:
A small strip of metal welded to the rods of the grid of the power section provide some extra cooling.
The connections from the electrodes to the base pins:
Another view, showing the heater wire going into the cathode of the high mu section:
The heaters of both sections are wired in parallel:
A close up:
The plates removed from their triode sections:
The grids and cathodes in comparison, power section on top and high mu section below:
Note the gold grid wire of the power section. The cathodes removed:
The grids in comparison:
A close up:
The high mu grid: