12B4A

Small Signal Triode — Noval

Known Equivalents & Substitutes

12B4

Similar Tubes (Not Drop-In Compatible)

Medium-mu single triode on B7G base — similar amplifier/driver application but 6.3V heater, higher ra (7700 ohm), and different base

Dual dissimilar triode on Noval base with 6.3V heater — power section has similar low-ra characteristics, used in similar vertical output service

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Max Plate Voltage550V

Peak Anode Voltage (max)Max Peak Plate Voltage1,000V

Anode Dissipation (max)Plate Dissipation (max)5.5W

Cathode Current (max)Max Cathode Current30mA

Typical Operating

Anode Voltage (typical)Plate Voltage150V

Grid 1 Bias VoltageGrid Voltage-17.5V

Anode CurrentPlate Current34mA

Anode ResistancePlate Resistance1,030Ω

TransconductanceTransconductance

Capacitances

Grid-to-Plate CapacitanceGrid-to-Plate Capacitance4.8pF

Grid-to-Cathode CapacitanceGrid-to-Cathode Capacitance5pF

Anode-to-Cathode CapacitanceAnode-to-Cathode Capacitance1.5pF

Heater

Heater VoltageHeater Voltage12.6V

Heater CurrentHeater Current0.3A

Notes

The 12B4A is an improved version of the 12B4 with tighter specifications. TDSL lists 12B4 as a different-rating substitute.
TDSL ratings: Va_max=550V, Pa_max=5.5W, Ik_max=30mA, Va_peak_max=1000V.
TDSL application data for frame (vertical) output: Va=150V, Vg=-17.5V, Ia=34mA, ra=1030 ohm, gm=6.3 mA/V.
Also available with 6.3V/0.6A heater — operated in series-string heater configurations in TV sets at 12.6V.
Mu is approximately 6.5 (derived from gm x ra = 6.3 x 1030/1000 = 6.5).
Popular in DIY audio as a low-impedance line-stage driver or headphone amplifier due to its low ra and high gm.

Pin Layout — Noval

1No Connection

2Plate

3No Connection

References