|Version: March 6, 2020|
Polycarbonate is a rather unusual material for phonograph cylinders, but this is what Ben Teo finally chose after trying out several other materials. The size he chose is 55 mm diameter, very nearly the old standard for phonograph cylinders. The polycarbonate pipe is held in place between two turned blocks of nylon.
The cutting head is driven by a 1.5-inch neodymium magnet speaker and runs along a feedscrew. The cutting stylus is made of titanium and it is specially shaped for cutting into a polycarbonate surface. And it is not only the choice of material for the cylinder that sets this phonograph apart; also, the groove is horizontally modulated. Like on a disc, the stylus moves sideways, not up and down.
The playback assembly rolls freely along a bar, driven only by the movement of the stylus in the groove. The cartridge used is of cheap quality. This is because the stylus of that cartridge is stiff enough to hold the weight of the whole playback arm. A higher quality cartridge has turned out to be too soft for this rugged technique. The horn on the side of the phonograph may seem odd for en electric playback machine, but it is actually driven by a loudspeaker inside the box.
A curious detail that attentive readers may have noticed is the positioning of the rubber belts on the pulleys: not centered, but on one edge. This is the natural position they take, and as they do not move from there, Teo has left them in place.
This player was built for a school open day under science department exhibitions: The Thomas Edison’s Great Inventions. It took almost 4 months to complete the project from design stage to idea realization.
Christer Hamp, 2020
|The phonograph in position for cutting. Stylus pressure can be controlled by varying the number of nuts on the M10 bolt at right, but just how much pressure that gives, nobody has measured.
|The cutting head folded up into playback position, the titanium stylus pointing upward. It is kept from accidentally falling down on the cylinder by the black wire at bottom.|
|The playback assembly does not use the feedscrew, but moves freeely guided by the stylus movement.||On the right hand side of the player are switches for the motor, recording amplifier, and playback amplifier, and knobs for volume, bass and treble control.|
All photographs provided by Ben Teo
|Write to Ben Teo:|