DV3 Audion De Forest with case – DL4 De Forest Audion – Type A – Type DE5 both by NELSON MULTI for the BBC

Description

We have already shown some De Forest Audion valves; this time we have a Mint still in its original metal case triode type DV3 Isolantite with ceramic base super rare!

The DL4 Designed as a special purpose RF amplifier-oscillator. First made 1926 with “Isolantite ” base.

Super rare Nelson top pip valves type A and DE5.

The Nelson Multi is a bright emitter triode with three straight wire tungsten filaments and a switching arrangement on the base thus giving double functionality.

One filament could be selected and thus provide three times the normal life for a low power valve operating as a detector or AF amplifier.

The instructions with the valve state:-

The valve contains three filaments which can be brought into use either one or two at a time, thereby lengthening the life of the valve and adapting it for power amplification.

The switch consists of two arms pivoted scissors-like on one of the cap legs. When it is desired to use one of the filaments the arms should be brought together with the tips in contact with one of the three studs in the valve base.

When two filaments are required the arms should be opened in opposite directions so that the tips are in contact with any two of the studs.