Pin-compatible but electrically different: mu=100 vs 70, Pa_max=1.0W vs 0.8W, heater current 0.3A vs 0.35A. Usable as a substitute in parallel-heater circuits with gain increase.
7025
Low-noise 12AX7 variant. Pin-compatible but mu=100 vs 70.
ECC83
European designation of 12AX7. Pin-compatible but mu=100 vs 70.
Electrical Specifications
Absolute Maximum
Anode Voltage (max)Max Plate Voltage330V
Anode Dissipation (max)Max Plate Dissipation0.8W
Cathode Current (max)Max Cathode Current4mA
Heater-to-Cathode Voltage (max)Max Heater-Cathode Voltage100V
Max Grid Resistor
Notes
Designed for military/avionics applications requiring resistance to shock (600g impact) and vibration (2.5g at 25 Hz). Features doubled bottom mica and dual top micas for mechanical stability.
The 5751WI is the full military specification version (MIL-E-1/746) with additional sweep-frequency vibration testing; electrically identical to the 5751.
Can substitute for 12AX7/ECC83 in parallel-heater circuits with approximately 30% gain reduction. Not a drop-in equivalent due to different mu, bias point, and heater current.
RCA characteristics range: mu 55-85, gm 900-1600 µmhos, Ia 0.4-1.8 mA at Va=250V. Wider tolerance range than typical receiving tubes reflects the military emphasis on reliability over tight parameter matching.
Registered October 1949 (Electron Tube Registration List). First documented by RCA, October 1953.
Pin Layout — Noval
1Anode 2 (Triode section 2)
2Control Grid 2 (Triode section 2)
3
Socket-Compatible Tubes ⚠ Not electrically compatible