EF37A

Small Signal Pentode — Octal

Mullard

Known Equivalents & Substitutes

CV358CV5080VR56

Similar Tubes (Not Drop-In Compatible)

American octal equivalent family — similar characteristics but different detailed ratings

EF36

Earlier version with higher noise — same base and similar ratings but EF37A has tighter noise spec

B9A successor with improved shielding and lower noise — different base, not pin-compatible

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)300V

Screen Voltage (max)Screen Voltage (max)200V

Anode Dissipation (max)Anode Dissipation (max)2W

Screen Dissipation (max)Screen Dissipation (max)0.5W

Heater-to-Cathode Voltage (max)

Notes

The EF37A is the 'A' revision of the EF37, with improved low-noise performance and more consistent manufacturing. Both are octal (IO/B8G) based.
Widely used in BBC and professional audio equipment in the 1940s and 1950s before being superseded by the EF86.
Pin 1 is the metallic screen/shield connection — must be grounded for lowest noise and hum.
Suppressor grid (g3) is brought out to a separate pin, allowing external connection. For pentode operation, connect to cathode.
Triode strapping is achieved by connecting g2 and g3 to anode. No triode-strapped data is available in the Schlangen reference for this type.
Datasheet not available from frank.pocnet.net; specifications from Mullard published data and cross-referenced with Brans Vademecum and Philips interchange tables.

Pin Layout — Octal

1Metallic Screen

2Heater

3Anode

4