EL34

Power Pentode — Octal

Philips

Known Equivalents & Substitutes

6CA7E34LEL34BEL34GCV17416P27S7534

Similar Tubes (Not Drop-In Compatible)

Beam tetrode with same Octal pinout. Often used interchangeably but EL34 is a true pentode with suppressor grid on pin 1, while 6550 has beam plates — different internal topology and somewhat different characteristics.

EL37

Same Octal base pentode, mutually listed as equivalent by Brans. Earlier Mullard design with slightly different characteristics. Verify ratings before substitution.

KT77

GEC beam tetrode on same Octal pinout — pin 1 is NC (beam plates) vs suppressor grid on EL34, different internal construction

Electrical Specifications

Section 1 — Pentode

Absolute Maximum

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

Screen Voltage (max)Screen Voltage (max)500V

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

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

Notes

In triode connection (g2 strapped to anode), Va_max increases to 600 V but combined Pa+Pg2 dissipation is limited to 30 W (Va ≤ 500 V) or 15 W (Va = 600 V).
PP triode (Rk bypassed): Vb = 430 V, Va = 400 V, Ra-a = 5 kΩ, Rk = 440 Ω/valve delivers 19 W at 1.8% THD. With Rk unbypassed: Ra-a = 10 kΩ delivers 14 W at 0.4% THD.
Pentode characteristics measured at Va = 250 V, Vg2 = 250 V, Vg1 = 0 V: Ia = 100 mA, Ig2 = 15 mA, gm = 11 mA/V, ra = 15 kΩ, μg2g1 = 11. Triode characteristics at Va = 250 V: Ia = 70 mA, Vg1 = -15.5 V, gm = 11.5 mA/V, ra = 910 Ω, μ = 10.5.

Pin Layout — Octal

1Suppressor Grid (g3)

2Heater

3Anode

4

Socket-Compatible Tubes ⚠ Not electrically compatible

KT66 KT88

References