EL12

Power Pentode — Y8A

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Telefunken

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Known Equivalents & Substitutes

EL12/325EL12spez

Similar Tubes (Not Drop-In Compatible)

6CM5

Functionally similar (American EL36 equivalent) but Octal base vs Y8A — not pin-compatible

EL12/375

Factory-selected variant rated for 375V operation — same Y8A base and pinout, but verify transformer voltage matches this rating

EL35

Related power pentode in the same Brans family — different base, not pin-compatible

EL36

Functionally similar but Octal base vs Y8A — not pin-compatible

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Anode Voltage (max, operating)350V

Screen Voltage (max)Screen Grid Voltage (max, operating)350V

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

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

Notes

Cathode-bias only — the datasheet explicitly prohibits fixed-bias operation.
Separate cathode resistors required per tube in push-pull configurations.
Va_max of 350V is the Telefunken/RFT rating; Philips/Valvo versions are conservatively rated to 250V. Variants with voltage suffix (/325, /375, /425) are factory-selected for higher voltages.
No pin-compatible equivalents; EL36/6CM5 is functionally similar but uses an Octal base.

Pin Layout — Y8A

1Suppressor Grid (internally connected to cathode)

2Screen Grid

3Control Grid

References

https://frank.pocnet.net/sheets/082/e/EL12.pdf

Cathode Current (max)

90mA

Heater-to-Cathode Voltage (max)Heater-to-Cathode Voltage (max)50V

Max Grid ResistorGrid Leak Resistance (max, Va≤250V)0.7MΩ

Max Grid ResistorGrid Leak Resistance (max, Va>250V)0.2MΩ

Typical Operating

Anode Voltage (typical)Anode Voltage250V

Screen Voltage (typical)Screen Grid Voltage250V

Grid 1 Bias VoltageGrid Bias (cathode resistor, approx.)-7V

Anode CurrentAnode Current72mA

Screen CurrentScreen Grid Current8mA

Anode ResistancePlate Resistance30,000Ω

TransconductanceTransconductance15mA/V

Cathode Resistor (self-bias)Cathode Resistor (self-bias, SE)90Ω

Output

Output PowerOutput Power (Class A, single-ended, k=10%)8W

Load ImpedanceOptimum Load Resistance3,500Ω

Capacitances

Grid-to-Plate CapacitanceGrid-to-Anode Capacitance<0.7pF

other

Screen Dissipation (max, driven)Screen Dissipation (max, driven)5W

Heater

Heater VoltageHeater Voltage6.3V

Heater CurrentHeater Current1.2A

Cathode

5Heater

6Heater

7Anode

8No Connection