Bakelite wonder

In the 1930's electrical amplification was a well established technology, widely used above all in radio receivers, which often also served as amplifiers for gramophones with electric pick-ups. In the late '20s recording technology had quickly become electrified at the same time as production of phonograph cylinders finally ceased and discs took over the market completely.

One of the people working to improve recording and reproducing technology was Adrian Sykes, who filed a number of patent applications in the field. One of his 1934 applications was for an attachment to be used with the floating weight and stylus from an Edison reproducer. This attachment replaced the membrane, soundbox and horn, converting the phonograph to an electric one, to be connected to a radio receiver.

The patent mentions Edison phonographs as the machines the attachment was intended for, but does not specify which models. In his collection, Rob Lomas has the device pictured here, made to fit a Diamond B reproducer used with the models Fireside, Standard, Home and Triumph.

The construction is an electromagnetic pickup pretty much as they were made at the time, with an iron rod moving inside a coil. The device can be adjusted in two ways, either by sliding the moving magnet up or down by turning a screw on top of the casing (86 in the figure below), or by adjusting the pressure of the plate clamping the rubber sheets around the armature (12 in the figure below).

It seems to be a sound construction, and today Rob Lomas finds it sounds "surprisingly good". It appeared on the market at an awkward time, however. It could not have been successful much earlier than the mid '30s, because only by then had amplified radio receivers become commonplace, but production of phonograph cylinders had ceased years before, and thus the Electrograph was at a dead end from day one. It is not known to me how many were produced or in which countries it was sold.

The text of the patent (British patent 439,800, accepted Dec. 16, 1935) distinguishes the following parts in the section view (fig. III):
4.	Cobalt steel magnet
6.	Polar extension
7.	Armature clamped between rubber sheets as at 12 or alternatively set in a rubber tube.
10.	Winding on a suitable bobbin
12.	Rubber sheets clamping the armature 7
67.	Floating weight, to be taken from the existing reproducer on the Edison phonograph [blue colour marking not in the patent]
68.	Diamond tipped stylus lever
72.	Brass crosshead soldered at or near the end of armature 7 and to which is attached a loop of thread, twisted or otherwise, wire link, cord or other transmission device engaging with the stylus lever 68
82.	Brass laminae connected to the terminals
83.	Nut supporting the electromagnetic system within the housing
84.	Nut supporting the electromagnetic system within the housing
85.	Distance washers providing an element of adjustment.
86.	A cap that engages with the central core of the pole and enables this to be rotated by hand and so vary the magnetic gap

As we can see, the description in the patent is not equal to the actual reproducer in all details, but it gives a good insight into its inner workings.

Christer Hamp, 2003

 
All photographs provided by Rob Lomas