← Reference

12AU7

also ECC82 · 12AU7A · 5814A · 5963 · B329

Medium-mu (µ=17) dual triode — the low-gain, low-impedance member of the 9A-based twin-triode family. Its job is rarely gain: it drives, buffers, or swings something that a high-mu valve could not. In the Vox AC15 it is the vibrato modulator, sitting across the phase-shift ladder and varying it under the oscillator's control, which is why the amp's vibrato bends pitch rather than merely chopping level.

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 12AU7A frank.pocnet.net ↗
Philips ECC82 frank.pocnet.net ↗
General Electric 12AU7A 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=-8.5 V → Ia=10.5 mA, gm=2200 µmho, µ=17
Source
RCA 12AU7-A data sheet / RCA Receiving Tube Manual RC-19, 1959, Class A1 average characteristics (rp=7700 Ω on the same row)
Note
Single-anchor fit at the tabulated 250 V point, on the same pattern as the 12AY7 and 12AT7 entries: MU=17 and EX=1.5 are fixed, KP and KG1 are solved so the model reproduces the published Ia and gm exactly at the anchor.
File
models/12au7.inc ↗

See these parameters drawn: the load line explorer plots the 12AU7's plate-curve family from this model and solves an operating point on it.

Maximum ratings

RCA prints these as design-MAXIMUM values, each unit — not the design-centre system the European sheets in this corpus use, so they are not directly comparable with the EL84 and EF86 entries: a design-maximum figure is the line an individual valve must never cross, where a design-centre figure already carries an allowance for spread. The 2.75 W per plate is nearly three times the 12AX7's budget, which is the point of the valve — it is built to pass current, not to make gain.

Plate voltage
330 V
Plate dissipation, either plate
2.75 W
Plate dissipation, both plates (both units operating)
5.5 W
Cathode current
22 mA
Peak heater-cathode voltage
200 V either polarity
Grid-circuit resistance, fixed bias
1 MΩ
Rating system
Design maximum — the line no individual valve may cross
Source
RCA 12AU7A data sheet, DATA 1, 7-61 — Class A1 amplifier maximum ratings (design-maximum values, each unit) ↗