VT-25A

Power Triode — DHT — UX4

Tung-Sol

Known Equivalents & Substitutes

Similar Tubes (Not Drop-In Compatible)

Similar DHT power triode with UX4 base but 2.5V filament and higher power output

Similar DHT power triode with UX4 base but lower filament voltage (2.5V) and different operating point

Earlier DHT power triode with UX4 base but lower mu and less output

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Anode Voltage (max, Class A)425V

Anode Dissipation (max)Anode Dissipation (max)12W

Typical Operating

Anode Voltage (typical)Anode Voltage (typical)350V

Grid 1 Bias VoltageGrid Bias Voltage-32V

Notes

The Type 10 (VT-25/VT-25A) is a directly heated power triode with 7.5V/1.25A thoriated tungsten filament. Maximum plate dissipation 12W in Class A.
Class A operation at Va=350V, Vg=-32V: Ia=16mA, mu=8, gm=1590 umhos, Rp=5150Ω, Po=0.9W (single-ended, 8% THD).
Class A at Va=425V, Vg=-40V: Ia=18mA, Rp=5000Ω, gm=1600 umhos, Po=1.6W.
Class B push-pull at Va=350V: Po=13W per tube, max Ia=55mA. At Va=425V: Po=20W.
The 801A is an improved version with higher plate voltage rating.

Pin Layout — UX4

1Filament

2Grid

3Anode

4Filament

Socket-Compatible Tubes ⚠ Not electrically compatible

References