← Reference

6CG7

also 6FQ7 · ECC186

Medium-mu (µ=20) nine-pin twin triode — electrically the 6SN7 rebuilt on a noval base when the industry left the octal behind, and rated to pass real current: 9 mA a section at 250 V, 4 W a plate. That is what the Danelectro-built Silvertone chassis wants in the two jobs a 12AX7 does badly, and it uses one for each: the split-load phase inverter that drives a pair of 6L6GCs, and the reverb driver that has to swing a tank. The 6FQ7 is the same tube with a controlled warm-up heater — the drawing letters the socket "6CG7 or 6FQ7" and means it.

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
  • No connection

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

⚡ 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 6CG7 tubebooks.org ↗

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 V → Ia=9 mA, gm=2600 µmho, rp=7700 Ω, µ=20
Source
RCA 6CG7 data sheet, 8-59, DATA 1, Class A1 amplifier characteristics (each unit)
Note
Single-anchor Koren fit at the 250 V column (KP, KG1 solved to reproduce the plate current and transconductance; MU=20 and EX=1.5 fixed, KVB at the project triode default because RCA's two columns move the grid voltage as well as the plate voltage and so constrain nothing about it). The sheet's other published rows are used as unfitted checks and their residuals are published rather than tuned away: at Va=90 V / Vg=0 V the model reads 8.42 mA against 10 mA printed and gm 2749 against 3000 µmho; at Va=250 V / Vg=−12.5 V it reads 1.43 mA against 1.3 mA; plate resistance at the anchor comes out 7.31 kΩ against the printed 7700 Ω, so effective µ at the anchor is 19.0 rather than 20.
File
models/6cg7.inc ↗

See these parameters drawn: the load line explorer plots the 6CG7's plate-curve family from this model and solves an operating point on it.

Maximum ratings

Design-maximum values, Class A1 amplifier, each unit. Two of them matter to the circuits in this corpus. The 330 V plate ceiling is low for a bottle sitting in an amplifier whose rectifier stack makes 480 V, so every 6CG7 socket in the Silvertone chassis is fed through a dropper and idles well under it. And the 1 MΩ grid-circuit limit for fixed-bias operation is exactly the value that chassis returns its inverter grid through — the drawing sits on the rating, not inside it.

Plate voltage
330 V
Plate dissipation, either plate
4 W
Plate dissipation, both plates (both units operating)
5.7 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 6CG7 data sheet, 8-59, DATA 1 (design-maximum values) ↗