We thought we would go in the opposite direction this week. One of the lowest power audio output valves is the DL96. Designed as part of the "25mA" series of directly heated valves for battery portable radios, which were popular in the 1950s, before transistors became commercially available. Here is the description from the National Valve Museum:
"The DL96 is an audio output valve from Mullard's low consumption dry battery valves from 1954. The audio output is low at 0.2 Watts but considering the low filament power it is quite remarkable.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 46 mm tall.Type DL96 was first introduced in 1953."
Unlike the other valves in the set (which can be operated as series 25mA or parallel 1.4V filaments) the DL96 has a centre tapped filament which could be configured for series 25mA at 2.8 volts or parallel 50mA at 1.4V to get the full 0.2 Watts of audio. There was an extra mode where it was possible to light up just one half of the filament but derive only 0.1 Watts of audio.
This example comes from a Pye battery portable radio, which we will feature on this page soon.
"The DL96 is an audio output valve from Mullard's low consumption dry battery valves from 1954. The audio output is low at 0.2 Watts but considering the low filament power it is quite remarkable.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 46 mm tall.Type DL96 was first introduced in 1953."
Unlike the other valves in the set (which can be operated as series 25mA or parallel 1.4V filaments) the DL96 has a centre tapped filament which could be configured for series 25mA at 2.8 volts or parallel 50mA at 1.4V to get the full 0.2 Watts of audio. There was an extra mode where it was possible to light up just one half of the filament but derive only 0.1 Watts of audio.
This example comes from a Pye battery portable radio, which we will feature on this page soon.
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