Amplifier, Modified, Ex US Military

Radford Electronics Ltd.; Bristol

  • Year
  • 1948 ?
  • Category
  • Audio Amplifier or -mixer
  • Radiomuseum.org ID
  • 360430

 Technical Specifications

  • Number of Tubes
  • 7
  • Main principle
  • Audio-Amplification
  • Wave bands
  • - without
  • Power type and voltage
  • Alternating Current supply (AC) / 110 Volt
  • Loudspeaker
  • - This model requires external speaker(s).
  • Material
  • Metal case
  • from Radiomuseum.org
  • Model: Amplifier, Modified, Ex US Military - Radford Electronics Ltd.;
  • Shape
  • Tablemodel, Box - most often with Lid (NOT slant panel).
  • Notes
  • In December 1948 Radford advertised surplus US military 25 W TG10 Keyer amplifiers modified to work with a microphone or gram and a transformer to work from 110 V to 230/240 V mains.

    This amplifier featured:
    Circuit Topology

    • Output Stage: Push-pull configuration using two 6L6 power pentodes, capable of delivering 25 watts RMS.
    • Phase Inverter: A 6N7 dual triode likely served as a split-load phase inverter, enabling balanced drive signals for the output stage.
    • Preamp/Driver Stage: Two 6J7 pentodes (possibly RF-type valves) handled initial signal amplification and tone control integration.
    • Power Supply: A 5U4G rectifier tube in a choke-input or capacitor-filtered design, originally configured for 110V AC. An optional auto-transformer allowed operation on 210–230V mains. 21/- extra.

    Key Features

    • Input Flexibility: Modified to accept microphone and gramophone inputs, with adjustable tone controls for broader usability.
    • Output Options: Multi-tap output transformer supporting 4 Ω, 8 Ω, and 15 Ω loads, reflecting adaptability for diverse speaker systems.
    • Low Distortion: Early emphasis on precision, with distortion levels low enough to necessitate custom measurement tools—a hallmark of Radford’s engineering rigor even in this era.
    • Cabinet: Mounted in a smart black crackle carrying case.
    • Price: £7/12/ 6 with valves.

    These designs laid the foundation for Radford’s later hi-fi innovations, combining pragmatic reuse of wartime hardware with thoughtful circuit optimisation.

  • Price in first year of sale
  • 2.63 GB £
  • Author
  • Model page created by Gary Cowans. See "Data change" for further contributors.

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