← Reference

5879

RCA nine-pin sharp-cutoff pentode, built for the one job its sheet names in the title: audio-amplifier applications critical as to microphonics, leakage noise and hum. That brief is what put it at the front of a Gibson combo, where a preamp valve sits a few inches from a twelve-inch speaker. It is a small valve for a small signal — 1.25 W of plate dissipation, 1.8 mA at the tabulated point — and it buys the gain of a pentode where a triode of the era would give several times less. Grid No.3 has its own pin and the sheet directs it to be connected to the cathode at the socket.

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 9AD

⚡ 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 5879 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, Vg2=100 V, Vg3=0 V, Vg1=-3 V → Ia=1.8 mA, Ig2=0.4 mA, gm=1000 µmho
Source
RCA 5879 data sheet, Data 1, 3-61 — Characteristics, Class A1 Amplifier, pentode-connection column
Note
µ=21 is the tabulated TRIODE-connection amplification factor standing in for the grid-No.1-to-grid-No.2 factor, which RCA does not print for this tube — the documented substitution METHODOLOGY.md allows, and the one the 6SJ7 and KT66 models already make. RCA prints 21 in both of its triode columns (Va=100 V and Va=250 V), so the figure at least holds across the sheet's own plate range. EX=1.5 and KVB=30 are the project pentode defaults: this sheet tabulates the pentode connection at ONE plate voltage only, so — unlike the 6SJ7 — nothing in the data measures the plate-voltage dependence.
File
models/5879.inc ↗

See these parameters drawn: the load line explorer plots the 5879's plate-curve family from this model and solves an operating point on it.

Maximum ratings

Design-maximum values. The pentode-connection column is the one that applies in this corpus's circuits; the triode column is the same valve with grid No.3 and grid No.2 tied to the plate, and is rated lower on the plate (275 V) but higher on dissipation (1.7 W). A quarter of a watt of screen input and 1.25 W on the plate keep this firmly a small-signal valve: the screen is fed through a dropper, never tied to the rail.

Plate voltage
330 V
Grid-No.3 (suppressor)
connect to cathode at socket
Grid-No.2 (screen) supply voltage
330 V
Grid-No.2 input
0.25 W for screen voltages up to 165 V (above that, the sheet's rating chart)
Grid-No.1 voltage, negative-bias value
55 V
Grid-No.1 voltage, positive-bias value
0 V
Plate dissipation
1.25 W
Peak heater-cathode voltage
100 V, either polarity
Grid-No.1 circuit resistance
2.2 MΩ
Plate voltage, triode connection
275 V
Plate dissipation, triode connection
1.7 W
Rating system
Design maximum — the line no individual valve may cross
Source
RCA 5879 data sheet, Data 1, 3-61 — Amplifier, Class A1, Maximum Ratings, Design-Maximum Values ↗