DO20 Mullard balloon very rare audio output triodes carbon plate oxide filament tested 100% pair

Description

The Mullard DO20 is one of the rarest and most sought after audio valve.

Introduced in 1929 for radio sets, it is nowadays used in DIY amps with excellent results.

You can get the sweetest 10 watts with such a valve.

The DO20 is a directly heated output valve for powerful receivers and amplifiers.

Filament voltage 7.5

Filament amps 1.30

Anode Volts 425

Anode mA 40

Grid -66

Gm 2.50

Both Mullard balloon have been tested at 45mA and 46mA with 100% emission.