M.O. Valve DE5a Dull Emitter Triode
Marconi DE5a Output Triode
The DE5a was introduced in 1925. The filament need 5 to 6 volts at a quarter of an amp. The recommended anode voltage was 60 to 120 volts. The DE5a was an improved lower impedance version of the DE5 introduced the previous year. Unlike the DE6, which had classic cylindrical electrodes, this valve has a box anode and a V shaped filament to increase the emission and hence the output power.
This valve arrived in its original box along with a receipt dated April 1926 from Marconiphone in Tottenham Court Rd. London for £1/6/0, equivalent to £215 today, based on average earnings.
