How the Wind-up Gramophone or Phonograph Worked
The Wind-Up Gramophone
When I was young, in the '50s, I lived in a house my Grandfather had bought around 1912. I never knew the old man—he died before I was born—but I knew lots of his prized possessions. My favourite among them was a large, cabinet-style, wind-up gramophone (or phonograph, in US) with a fine collection of records that he'd acquired over the years. The records we later referred to as "seventy-eights," because 78 r.p.m. was their rotational speed on the turntable, but that was a distinction we made only later, when 45s and 33s came along. In those days, they were just called "gramophone records."
A Mechanical Marvel
The gramophone in the picture above is similar to the one we had. Younger readers might be surprised to hear that you didn't plug it in. No electricity, no electronics. Here's how you used it.
- Raise the lid to access the turntable.
- Open the bottom cabinet and select your record. (The lower half was just for storing your music collection).
- Wind up the motor using the handle on the right side of the cabinet. The clockwork motor could play eight to ten songs before needing to be rewound.
- Place the record on the turntable and place the needle (it wasn't called a stylus then) in the take-up groove at the outer edge of the record.
- Open the upper pair of doors to let the sound out. The top doors were the only way to control the volume in these old mechanical gramophones!
- Operate the start lever to play the record.
Because of the high turntable speed and the coarse groove pitch, a ten-inch record only lasted two and a half minutes per side. This is why the popular songs of the era were never longer than two and a half minutes. If it wouldn't fit on a record, it wouldn't sell.
How Did it Work?
A hundred years ago, microphones, amplifiers, and loudspeakers hadn't been invented, or at least they were still in the laboratory stage, so music had to be recorded and played back acoustically. A record's groove was not perfectly smooth, but carried the imprint of the original sound wave in the form of a microscopic, side-to-side meandering in the groove. The needle followed this meandering more or less faithfully, and the resulting vibration was transferred by mechanical coupling to a small circular diaphragm mounted vertically in the head of the tone arm. The tone arm was hollow and made of brass. It carried the sound down below the turntable to a flared plywood horn that had its mouth just behind the top doors mentioned earlier. The exponential horn is often wrongly described as an acoustic amplifier. It is, in fact, an acoustic transformer, coupling the vibrational energy of the diaphragm more efficiently with the surrounding air. (Trumpets and trombones work exactly the same way.)
Slow, Slow, Quick, Quick
Another wonder of this old machine was that it could play about twenty minutes of music on a single wind-up, without ever slowing down. Then, suddenly, it would slow down and stop all in a few seconds. It managed this because in the heart of the clockwork motor was a beautiful little device called a centrifugal governor. This technology had actually been around for over a hundred years, controlling the speed of steam engines. The governor is driven at speed by the motor and is geared up. This causes the brass balls to swing outwards and upwards on their pivoted arms. The upwards movement lifts a collar, which is in turn coupled to (in the case of a steam engine) a steam valve, or (in our humble gramophone) a simple, felt friction pad. The net effect is the same: The faster it tries to go, the more it is held back, resulting in constant speed from fully wound to almost fully unwound.
Let the Music Play!
Just a Few Facts
- The tone arm had to be heavy because, with no amplification, all the energy had to come directly from the needle in the groove.
- A needle lasted only for about six plays, then it was too blunt to follow the groove.
- Needles were graded loud, medium, or soft. They came in little metal boxes of 100.
- Before 78 rpm was standardised, records were made to play at a range of speeds. 76 and 80 were not uncommon. Some even played from the inside out.