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Valve Gallery - Triode Amplifiers (1)

Valves: 210HL, AC/HL, MH4, MHD4.

Shown above is a Cossor 210HL. This valve has a B4 base with 2v heater. With a height of 100mm it has an amplification factor of 24. This valve is from the late 1920s and the paper label in use by Cossor at that time may be seen.

Shown above is a AC/HL triode valve from Mazda. With the large balloon envelope this again was the earliest incarnation of this valve. With a B5 base it has a height of 136mm, heater voltage of 4v and amplification factor of 35.

Shown above is an MH4 from Marconi Osram. Clearly this is another valve from their "Catkin" range. The Catkins are further considered here. This triode has a B5 base with 4v heater. It has an amplification factor of 40 with height of 114mm.

Shown above is a Marconi Osram MHD4. This too has an amplification factor of 40, but the envelope also contains two diodes. As there would be insufficient pins on a B5 base a B7 base is utilised with top cap. The valve is not able to handle quite so much current as the plain MH4 either. Height of 131mm with 4v heater.

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