Electromechanical amplifier (carbon amplifier)
Black ebonite base with the speaker transformer hidden inside and on top of the carbon amplifier itself.

The input signal is fed through two connections to a coil, causing a metal rod (acting as a diaphragm) to vibrate in rhythm with the sound signal. The rod is connected to a carbon microphone that is connected to a 3 volt battery. The current is amplified and fed via a transformer to a connected horn loudspeaker. The Brown company already came up with such a system, both as a single unit and built into a horn loudspeaker, the Crystavox. In 1926 Brown came up with a version that amplified the sound an extra time via an extra coil set and carbon microphone. This Brown Crystal Amplifier with two microphones from 1926 is shown on the right.
The advantage of this type of amplifier was that it was a lot cheaper than a tube amplifier; 38 shillings versus about 10 pounds. A disadvantage was that the distortion was somewhat greater.

The electromechanical amplifier was invented in 1904 by the American Bell engineer Herbert E. Shreeve (he was born in England). He used the system (left) to amplify the telephone signals between New York and Chicago. The Microphone Bar Amplifier can amplify the weak signal from a crystal receiver. It operates on two 1.5 volt dry cells. It was made by New Wilson Electrical Manufacturing Co., Ltd., 18 Fitzroy Street, Euston Road, London W1.
The original price was 38 shillings.
Serial number: none
Dimensions (h x w x d): 11.5 x 9.5 x 9.5 cm
Made in: 1926
Purchased in: 2011
Impedance: 2000 ohms


The amplifier with disconnected bar Back

This page was last edited on 04.02.2021