Virtual Valve Museum
Virtual Valve Museum | search: (use * for wildcard)
About the museumMuseum exhibitsUpdates, new exhibits etc.EquipmentSupporters
View the guestbookDocumentsValves wanted!Valves for sale or for tradeLinks to other sites, suppliers etc.

American RETMA designation system

Figure group, letter group, figure group (plus additional letters): eg 12AU7

1st figure group: filament or heater voltage

7 and 14 are nominal ratings; actual voltage for '7' should be 6.3 and for '14' should be 12.6.

0 Cold cathode
1 Between 0.1 and 2.1
2 Between 2.1 and 2.9
3 Between 3.0 and 3.9
5 Between 5.0 and 5.9
6 Between 6 and 6.9
7 Between 7 and 7.9

Letter group: letter(s) indicate the serial order of assignment of the designation.

Letters U, V, W, X, Y and Z are commonly used for rectifiers

S as a first letter indicates single-ended tubes, related to grid-cap tubes.

S as a second letter indicates single-ended tubes.

Combinations like AB, AC, AD and AE were used when all the single letters were used up.

L as a first letter often indicates a lock-in (Loktal) valve.

P as a second letter indicates a CRT.

Wherever possible, the 12V equivalent of a 6V tube had the same letters, just 12 instead of 6.

2nd figure group is the number of useful elements; in metal tubes the shell counts as one element. Base shielding does not count.

Additional letters:

A, B, C Improved backward compatible versions
E Export version
G Glass bulb, ST-12 to ST-16 size
GC Glass Compact
GT Glass bulb, T-9 size
GT/G Glass bulb, T-9 size interchangeable with G and GT types
L Loktal
LM Loktal-metal
LT Locking base
M Metal envelope
MG Metal-glass
ML Metal-Loktal
S Spray shielded
W Ruggedised
WA High quality version
X low loss ceramic base for HF use
Y low loss phenolic base for HF use

This file was last modified 16:45:23, Thursday August 28, 2014