PX4 Osram early 1930s slanted plate balloon shaped tested 100% AC044 PP3/250 equivalent

Osram balloon 1930s valves type pX4 £ 1,200 pair


The PX4 is a super-power output valve for powerful receivers, capable of driving moving coil and large speakers at full volume.

Type PX4 is a directly heated power triode for the output stage of receivers and amplifiers where a considerable undistorted power output is required with an anode voltage up to 300. For this purpose the PX4 valve has exceptionally good characteristics  and is particularly suitable for operating moving coil speakers at large volume without distortion.

The filament of the PX4 is of the robust oxide coated type and may be heated from A.C. through a suitable step-down transformer

Filament Voltage 4

Filament Current 1.0 amp

Anode Voltage 300

Grid Voltage -42

Anode Current Average 50mA

AudioMagical tries to cover all PX4 type made from the beginning of 1929 up to the 1960s.

Holy Grail of audio valves! The early Osram PX4 balloon shaped with slanted plate at 45  is among the best valve ever made by the Marconi Osram works.

Here we have a pair early 1930s balloon shaped.

Blue and black  on glass.

Excellent sounding valves with full cup getter.

Both Osram PX4 balloon have been tested with AVO 163 at:

Osram PX4  balloon {1}: 52mA 100% emission

Osram PX4 balloon {2}: 53mA 100% emission

Supplied with provisional boxes.


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