Elwell Amplifying Unit

The Elwell Amplifying Units, introduced in 1922, were modular valve amplification components that combined a valve holder with a fully enclosed intervalve transformer in a single patented assembly. Designed for convenience and reliability, each unit provided one complete stage of amplification without requiring soldering or external transformer wiring.

Design and Construction

• The unit consisted of an ironclad intervalve transformer and valve socket mounted together, with all permanent connections pre-made and embedded in insulating compound.
• Grid connections were given extra-long leakage paths and full insulation to reduce unwanted "howling" and noise, a common problem in amateur receivers of the period.
• The transformer was encased in iron, allowing several units to be mounted close together without acoustic feedback effects.
• Provided with tapped fixing holes on two sides and the base, the units could be panel-mounted, shelf-mounted, or left freestanding.

Function and Variants

• The primary version, marketed as a "note magnifier," offered straightforward audio-frequency (AF) stage amplification.
• Alternate variants included an oscillation amplifier and a rectifying unit, enabling different circuit functions using the same modular construction.
• Multiple amplifying units could be linked, with two or more stages coupled together for greater signal gain.

Electrical and Practical Features

• Operation required only inserting a valve and connecting external leads to the clearly marked screw terminals.
• No soldering was necessary, making them especially suitable for amateur constructors and small-scale manufacturers.
• Self-contained permanent connections and compound embedding ensured long-term reliability.
• The valve holder incorporated an earth clip for secure grounding and silent operation.
• Price (1922): 39 shillings 6 pence (excluding valve).

Donde encontrará 11 modelos, 10 con imágenes y 1 con esquemas.
Ir al listado general de Elwell, C. F., Ltd.; London