Amplifier, Modified, Ex US Military

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.

Vous pourrez trouver sous ce lien 32 modèles d'appareils, 25 avec des images et 10 avec des schémas.
Tous les appareils de Radford Electronics Ltd.; Bristol