The Emerson 6SN7GTA tube is a glass octal type used as a
phase inverter or
resistance-coupled amplifier in radio equipment.
Like all other 6SN7GTA's it requires an octal socket and
may be mounted in any position. Each triode unit is
independent of the other except for the common heater.
The 6SN7GT tube type was formally registered in 1941 by
RCA and Sylvania. The 6SN7GT type is essentially two
6J5-type single-triodes within a single envelope.
The 6SN7A and 6SN7W were both short-lived designations
for 6SN7GTs made to military specifications. Their
construction included an additional ‘free-standing’
support post between the micas for greater vibration
tolerance. It is likely that there were little, if any,
additional selection criteria imposed upon A and W
designations that were not already fulfilled by GT
specifications. These designations used from
(approximately) 1941 to 1945.
The 6SN7GTA and GTB versions were introduced in 1950 and
1954 respectively. They have ‘upgraded’ ratings, which
are as follows:
GTA: maximum anode dissipation upgraded to 5W (the GT is
rated for 2.5W)
GTB: identical to the GTA, but with a controlled
heater warm up time for use in equipment with 600mA
heater strings
This is significant because it means that a circuit
designed around the 6SN7GTA/GTB cannot have 6SN7GTs
substituted into it. Substituting a GT in place of
a GTA / GTB in your equipment will precipitate its
rapid destruction and possibly damage your equipment.
Tubes labeled 6SN7GTC were made in the late 60s
and early 70s. They are electrically identical to
6SN7GTBs but have their glass envelopes replaced by
black colored metal envelopes. These tubes were mostly
manufactured in South America.
Electrical Data:
Heater Voltage ................................ 6.3 V
Heater Current ................................ 0.6 A
Maximum Heater-Cathode Voltage Heater Positive with
Respect to Cathode
DC Component ................. 90 V
Heater Negative with Respect to Cathode
DC Component ................. 90 V
Preferred Substitutes ................ 6N8S,
6SN7GTA, 13D2, B65, CV1988
Substitutes ...................... 6BL7, 6BX7GT