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 →).
Hover, tap, or focus a pin to name it.
- High voltage (B+)
- Control grid
- Cathode
- Heater / filament
Viewed from below (socket / wiring side) · octal · basing 8KG
⚡ 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.
| Publisher | Type | Source |
|---|---|---|
| Tung-Sol | 7591 | frank.pocnet.net ↗ |
| Sylvania | 7591 | frank.pocnet.net ↗ |
| Westinghouse | 7591A (April 1, 1963; JEDEC release | 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=300 V, Vg2=300 V, Vg1=-10 V → Ia=60 mA, Ig2=8 mA, gm=10200 µmho
- Source
- Tung-Sol 7591 data sheet, March 1, 1961 (plate #6125) — Typical Operation, Class A1 Amplifier
- Note
- µ=16.8 is the amplification factor printed beside this operating point, where it is labelled the triode amplification factor — the same substitution for the grid-No.1-to-grid-No.2 factor that the KT66 model makes, and the only amplification factor any of these publishers prints. Ia, Ig2 and gm are all tabulated at the one point, so KP, KG1 and KG2 anchor there together. EX=1.5 and KVB=30 (pentode) are project defaults per METHODOLOGY.md.
- File
- models/7591.inc ↗
See these parameters drawn: the load line explorer plots the 7591's plate-curve family from this model and solves an operating point on it.
Maximum ratings
Design-maximum values. The screen figure carries its own footnote: grid-No.2 dissipation may reach 6 W during the peaks of speech and music, and for the screen to work efficiently its two pins (4 and 8) must be tied together outside the socket. Cathode current is capped at 85 mA, which is what actually limits a cathode-biased pair.
- Plate voltage
- 550 V
- Grid-No.2 (screen) voltage
- 440 V
- Plate dissipation
- 19 W
- Grid-No.2 dissipation
- 3.3 W · 6 W on speech and music peaks
- Cathode current
- 85 mA
- Grid-No.1 circuit resistance
- 0.3 MΩ fixed bias · 1.0 MΩ self bias
- Heater-cathode voltage, heater negative
- 200 V total DC and peak
- Heater-cathode voltage, heater positive
- 100 V DC · 200 V total DC and peak
- Rating system
- Design maximum — the line no individual valve may cross
- Source
- Tung-Sol 7591 data sheet, March 1, 1961 — Ratings, interpreted according to the design maximum system; identical on Sylvania Engineering Data Service 7591, October 1961 ↗