← Reference

6SQ7

also 6SQ7GT · 6SQ7-GT/G

Octal double-diode high-mu triode — two diode plates and one µ=100 triode in one envelope, all three sections sharing a single cathode. It is the classic radio detector-plus-first-audio bottle, and in the Gibson GA-40 it is the triode alone that works: a phase-shift tremolo oscillator whose output modulates the screen and supply of the channel-2 preamp pentode. The two diode plates are unused there. This file exists so the drawn socket pins validate against the real basing — no SPICE model is carried, because no netlist in this corpus simulates the tube (a running oscillator has no static operating point to check).

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

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

  • High voltage (B+)
  • Diode plate
  • Control grid
  • Cathode
  • Heater / filament
  • Internal connection

Viewed from below (socket / wiring side) · octal · basing 8Q

⚡ 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 6SQ7, 6SQ7-GT/G frank.pocnet.net ↗
Tung-Sol 6SQ7, 6SQ7GT frank.pocnet.net ↗

Circuit Codex model

No SPICE model is carried for this valve. Nothing in the corpus simulates it: the one circuit that uses it runs it as a tremolo oscillator, which has no static operating point a DC model could be checked against. The basing above is what this archive asserts about it, and the socket wiring on the board drawing is validated against that. How the models are derived →

Maximum ratings

Design-centre values, and deliberately short: neither the RCA nor the Tung-Sol sheet prints a plate-dissipation rating for this bottle, so none is stated here. What both do print is a 300 V plate ceiling and a heater-cathode limit — 100 V on the RCA sheet, 90 V on the Tung-Sol one, which is the tighter of the two and the figure a builder should work to. The typical operation both give is the resistance-coupled amplifier chart for the Type 75, where the triode idles under a milliamp; this is a detector and first-audio valve, not a driver.

Plate voltage (triode unit)
300 V
D-C heater-cathode potential
100 V (RCA); 90 V (Tung-Sol)
Heater
6.3 V, 0.3 A, coated unipotential cathode
Amplification factor (triode unit)
100
Plate resistance
110 kΩ at 100 V; 91 kΩ at 250 V
Transconductance
900 µmho at 100 V; 1100 µmho at 250 V
Diode current, each plate, continuous
1.0 mA (Tung-Sol)
Plate dissipation
not printed on either cited sheet
Rating system
Design centre — carries an allowance for manufacturing spread
Source
RCA 6SQ7, 6SQ7-GT/G data sheet, Dec. 1 1943, "Maximum Ratings Are Design-Center Values — TRIODE UNIT"; Tung-Sol 6SQ7, 6SQ7GT sheet, Dec. 1 1947, "RATINGS (interpreted according to RMA standard M8-210)". ↗