EL12/425 — Power Pentode, Y8A | Tubeofile

EL12/425

Power Pentode — Y8A

Siemens

Known Equivalents & Substitutes

No known equivalents. If you know of any, use the ⚑ Report Issue button above.

Similar Tubes (Not Drop-In Compatible)

Standard version rated to 250 V (Philips) / 350 V (Telefunken) — same Y8A base and pinout

EL12/325

Lower voltage-selected variant — same Y8A base and pinout

EL12/375

Lower voltage-selected variant — same Y8A base and pinout

Electrically equivalent (RFT successor) rated for 425 V but different pin assignments on Y8A base — not pin-compatible

Electrically equivalent with top-cap anode, rated for 425 V — different pin assignments, not pin-compatible

EL150

Closely related Telefunken variant — same Y8A base

EL6/425

Electrically similar Philips equivalent but uses B8A base instead of Y8A — not pin-compatible

F2a11

Successor design — different base, not pin-compatible

Electrical Specifications

Section 1 — Pentode

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)425V

Screen Voltage (max)Screen Voltage (max)425V

Anode Dissipation (max)Anode Dissipation (max)18W

Screen Dissipation (max)Screen Dissipation (max, quiescent)2.5W

Notes

The '/425' suffix indicates factory selection for Va_max = 425 V operation — the highest voltage variant of the EL12 family.
Cathode-bias only — fixed bias is prohibited, same as all standard EL12 variants. Separate cathode resistors required per tube in push-pull configurations.
Used in Siemens/Telefunken Klangfilm cinema and broadcast amplifiers.
Late production, very rare according to Radiomuseum.
Stopper resistors recommended: at least 1000 Ω before control grid and 100 Ω before screen grid to prevent VHF parasitic oscillation.
Triode-strapped data (mu=18, ra=1.1 kΩ, gm=15 mA/V) sourced from diyAudio forum discussions on the EL12N family — values are consistent across the EL12/EL12spez/EL12N family.

Pin Layout — Y8A

1Suppressor Grid (internally connected to cathode)

2Screen Grid

3Control Grid

Socket-Compatible Tubes ⚠ Not electrically compatible

References