← Reference

12AT7

also ECC81 · 6201 · 6679 · B152

High-mu (µ=60) twin triode with low plate resistance and high transconductance — a strong current driver. In this archive it does the two jobs a plain 12AX7 does poorly: the low-impedance reverb driver that swings the tank transformer, and the long-tailed-pair phase inverter feeding the output tubes.

Basing (pinout)

Bottom view — the socket as you see it from the wiring side. Hover, tap, or focus a pin to name it. Read from the datasheet basing diagram (how to read these →).

1 2 3 4 5 6 7 8 9

Hover, tap, or focus a pin to name it.

  • High voltage (B+)
  • Control grid
  • Cathode
  • Heater / filament

Viewed from below (socket / wiring side) · noval 9-pin (B9A) · basing 9A

⚡ Oxblood pins sit at B+ — hundreds of volts in service, lethal, and still charged after power-off.

Datasheets

Primary manufacturer data, via public tube-data archives. The model below is fitted to the tabulated "average characteristics" in these sheets; the datasheet files themselves are linked, never rehosted.

PublisherTypeSource
RCA 12AT7 frank.pocnet.net ↗
General Electric 12AT7 frank.pocnet.net ↗
Mullard ECC81 frank.pocnet.net ↗

Circuit Codex model

A CC0 ngspice model in the Koren form, fitted here to the published anchor — no parameters copied from other model collections. Methodology →

Anchor
Va=250 V, Vg=-2.0 V (200 Ω cathode bias) → Ia=10 mA, gm=5500 µmho, µ=60
Source
RCA 12AT7 data sheet, March 1, 1954, tabulated Class-A1 characteristics
Note
Single-anchor Koren fit at the 250 V tabulated point (KP, KG1 solved to reproduce the plate current and transconductance; MU=60 and EX=1.5 fixed). The sheet's second tabulated point — Va=100 V, 270 Ω cathode bias → 3.7 mA, 4000 µmho — corroborates µ=60 and is not separately fitted.
File
models/12at7.inc ↗