12AU7 — Small Signal Triode, Noval | Tubeofile

12AU7

Small Signal Triode — Noval

Known Equivalents & Substitutes

ECC8212AU7A12AU7WAB329CV491CV4003CV10323CV10666CV8155CV8221M813658145814A596360676189668074897730E2163E82CCB7496AU7

Similar Tubes (Not Drop-In Compatible)

Same Noval dual triode pinout but higher mu (mu=60); lower plate current, higher ra — commonly used as phase inverter

Same Noval dual triode pinout but high-mu (mu=100); much lower plate current, used as voltage amplifier

Same Noval dual triode pinout, medium-mu (mu=44); popular in early Fender guitar amp preamps

Same Noval dual triode pinout, medium-mu (mu=70); military grade, sometimes used as lower-gain 12AX7 substitute

Medium-mu dual triode (mu=20) but Octal base; similar electrical characteristics, widely used in audio

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Max. Plate Voltage300V

Anode Dissipation (max)Max. Plate Dissipation (each section)2.75W

Cathode Current (max)Max. Cathode Current20mA

Heater-to-Cathode Voltage (max)Max. Heater-Cathode Voltage200V

Notes

One of the most widely used dual triodes, introduced in 1946. The 12AU7 family is the workhorse medium-mu type for audio phase inverters, cathode followers, and line stages.
The 5814A is the industrial/military premium version with controlled characteristics and tighter tolerances.
The 6189/12AU7WA is the ruggedized military version per MIL-HDBK-213A.
The E82CC (Telefunken/Siemens) and ECC802S (Tesla) are special-quality long-life European equivalents.
Can be operated with 6.3V or 12.6V heater supply using the pin 9 center tap.
Max grid resistor drops to 0.25 MΩ for fixed-bias operation (vs 2.2 MΩ for cathode bias).
At Va=100V, Vg=0V operating point: Ia=11.8mA, ra=6500Ω, gm=3.1mA/V, mu=20 — useful for low-voltage designs.

Pin Layout — Noval

1Anode 2 (Triode section 2)

2Control Grid 2 (Triode section 2)

Socket-Compatible Tubes ⚠ Not electrically compatible

References