Valve Gallery - Triode Amplifiers (2)

Valves: TDD4, ECC31, EBC3, HL23DD.

Shown above is a Mullard TDD4, which is Mullards equivalent of the MHD4 previously seen.  Again two diodes are included within the envelope.  4v heater with amplification factor of 27. Height of 135mm with B7 base.  Shown above is a Mullard ECC31.  This valve is notable for having two separate triode sections within the same glass envelope.  International Octal (I.O.) base with heater of 6.3v.  Amplification factors of 32.  Height of 105mm.

Shown above is an EBC3 from Mullard.  P Type side contact base, which seems to have contributed to a lack of focus again.  95mm height, 6.3v heater and amplification factor of 30. Shown above is a Mazda HL23DD.  This uses a Mazda Octal base. 102mm height, amplification factor of 32.  The metalised glass envelope also contains two diodes.  Heater voltage of 2v, this valve was designed for battery or portable receivers.  Mazda often sprayed metalised valves designed for battery sets green so they were easily recognisable.

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