Editing Nuvistor (section)

==Pin layouts==
Nuvistor sockets have a standardized layout based on four imaginary concentric circles with the pins laid out at 60 degree angles from the center point of the base.  The metal shell has two fins that extend below the base; the larger of these two fins is the key position. Sockets can accommodate up to 12 pins, but usually only five or six are used.

Pins 1, 2 and 3 are assigned to the outermost circle, with Pin 1 located 60 degrees clockwise of the key fin.  Pin 2, which is in line with the small fin, is 120 degrees clockwise of Pin 1.  Pin 3 is 120 degrees clockwise of pin 2.  For triodes, these pins (usually just Pin 2) are the plate/anode connection.  For tetrodes, one of these pins is the screen grid connection and the plate/anode has a top cap connection.

Pins 4, 5 and 6 are assigned to the next circle.  Pin 4 is in line with the key fin.  Pin 5 is 120 degrees clockwise of Pin 4 and the key fin.  Pin 6 is 120 degrees clockwise of Pin 5.  The pins in this circle (usually pin 4) connect to the control grid.

Pins 7, 8 and 9 are assigned to the next circle.  They are in the same lines as Pins 1, 2 and 3 and also increase in order going clockwise.  These pins (usually pin 8) connect to the cathode.

Pins 10, 11 and 12 are assigned to the innermost circle.  They are in the same lines as Pins 4, 5 and 6 and also increase in order going clockwise.  These pins (usually Pins 10 and 12) connect to the heater.

Base 12AQ -- which is used by most triodes, including 6CW4 and 6DS4 -- is the most common connection layout.  The connections are:
*Pin 2 - Plate/anode
*Pin 4 - Grid
*Pin 8 - Cathode
*Pins 10 and 12 - Heater

Base 12AS is the tetrode layout.  The connections are:
*Pin 2 - Grid 2
*Pin 4 - Grid 1
*Pin 8 - Cathode
*Pins 10 and 12 - Heater
*Top cap - Plate