EL38 — Power Pentode, Octal | Tubeofile

EL38

Power Pentode — Octal

Mullard

Known Equivalents & Substitutes

6CN6CV450CV80385P29EL38M

Similar Tubes (Not Drop-In Compatible)

Series-heater equivalent (300mA) — not compatible with 6.3V parallel heater circuits

Electrical Specifications

Section 1 — Pentode

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)800V

Screen Voltage (max)Screen Voltage (max)400V

Anode Dissipation (max)Anode Dissipation (max)25W

Screen Dissipation (max)Screen Dissipation (max)8W

Cathode Current (max)Cathode Current (max)

Section 2 — Triode Strapped

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)400V

Anode Dissipation (max)Anode Dissipation (max)25W

Cathode Current (max)Cathode Current (max)200mA

Typical Operating

Anode Voltage (typical)Anode Voltage300V

Heater

Heater VoltageHeater Voltage6.3V

Heater CurrentHeater Current1.4A

Notes

Anode connection is via top cap, not through the octal base.
Originally designed for TV line output (horizontal deflection) service, not audio. The anode can withstand peak pulses up to 8 kV in deflection circuits.
For audio service, do not exceed approximately 22 W static anode dissipation despite the 25 W maximum rating — localised hot spots on the anode have been reported at higher sustained dissipation.
Max grid resistor depends on anode dissipation: 500 kOhm when Pa < 25 W, 800 kOhm when Pa < 9 W.
PL38 is a near equivalent with a different heater voltage (300 mA series heater). EL38M is a slightly different variant.
Philips datasheet provides a second operating point at Va = 600 V, Vg2 = 400 V: Ia = 42 mA, Ig2 = 5 mA, Vg1 = -22 V, gm = 7.0 mA/V, ra = 43 kOhm.
Triode-strapped data (mu, gm, ra) sourced from Tom Schlangen's 'Pentodes Strapped as Triodes' table (2009) and estimated operating point from Patrick Turner via rec.audio.tubes (https://rec.audio.tubes.narkive.com/12sQdJgo/el38-6cn6-triode-strapped-data), not from the manufacturer datasheet.
No audio output power or load impedance is specified in the manufacturer datasheets for pentode mode — the tube was rated only for deflection service.

Pin Layout — Octal

1Suppressor Grid

2Heater

3No Connection

Socket-Compatible Tubes ⚠ Not electrically compatible

References