My DIY gramophone is an anachronistic mish-mash of old
and recently-made parts.
The motor, turntable, tone-arm and sound-box are from the late 1920s.
The rest, isn't!
Gramophone enthusiasts in the 1920s were just as keen to improve
their equipment as hi-fi enthusiasts are today.
In 1925, 'The Gramophone' magazine described, and sold, a gramophone accessory
called the 'Lifebelt'.
This was a flexible rubber coupling that fitted between the tone-arm and sound-box.
It was claimed to make music 'less shrill' and 'more resonant'.
You could buy one for 5/-.
Today, it is difficult to tell how flexible it was.
My version of the Lifebelt is very flexible. It's a length of car heater hose.
I had to use an extra piece of rubber to stop 'sound-box sag'.
The Lifebelt decouples the sound box from the tone-arm, reducing the amplitude of low-frequency vibrations reaching the diaphragm.
This gives the sound-box an easier time, as it has to deal with a more limited frequency range.
The horn cuts off the lower frequencies anyway.
Also, high frequency vibrations are prevented from travelling along the tone-arm,
which may be the reason for less 'shrillness'.
In the 1960s, Sonotone used a similar system in their 8T ceramic cartridge,
to reduce the audibility of rumble from autochangers.
I have tried about eight different types of sound-box.
The HMV 5A sounds best in my machine.
Having said that, some 5As sound better than others, I am not sure why.
I am also not sure if there should be a difference in sound between the 5A and 5B, as they look pretty much identical.
I have made an adjustable counterbalance, based on Percy Wilson's design for 'The Gramophone'.
This balances out the weight of the Lifebelt.
You could buy one for 7/6.
Wilson's book, 'Modern Gramophones and Electrical Reproducers' (1929),
is essential reading!
By 1927, the year the 5A was introduced, the Lifebelt was beginning to drop out of favour.
Around this time, many gramophone enthusiasts replaced their old gramophones
with new ones designed to play the latest electrically-recorded records.
These new, improved gramophones didn't benefit so much from an extra rubber hose.
Also, the easily-counterbalanced gooseneck tone arm was becoming less common.
I made a Quincke tube for the tone-arm, using a thin-wall brass tube with a nylon plunger.
The Quincke tube is described by Lord Rayleigh in 'The Theory of Sound'.
It's a quarter-wave resonator, which acts as a high frequency notch filter.
It's an interesting device, and it does work, but my gramophone doesn't benefit much from a cut at high frequencies!
I usually turn the horn sideways, in the same direction as the soundbox diaphragm.
The diaphragm then acts like a tweeter speaker.
In most cabinet gramophones, the sound from the diaphragm is not wanted,
hence 'Close Lid Whilst Playing'.
The tone-arm is from a cabinet gramophone.
It's upside down, with the crook reversed.
The tone-arm bearings were originally a pair of large plain brass washers.
I replaced these with PTFE washers.
The brass weight sticking out the back balances the weight of the tone arm
when the needle is on the record. This ensures even pressure on the bearing, so no air leaks.
The back bracket is a one-off alloy casting.
The horn has an exponential profile. Perhaps it should have been longer!
It is papier-mâché, laid up on a wood and plaster former.
The sound is pretty good, more by luck than judgement.
I once tried using a large public-address horn connected directly
to a 5A sound-box. I expected great things, but it sounded terrible.
The motor is a Garrard 11A.
It could do with some attention, as it is making an 'rrrrrrrr' sound.
The 'stereo' microphone doesn't seem to be working.
Sounds like mono to me.
The record is 'Dusty Shoes', by Turner Layton. Columbia.
Recorded in 1934 (Thanks to transformingArt for this info).
The needle is a steel 'soft tone'.
In my next recording, which sounds quite a bit better, I use a fibre needle:
• The Foggy Foggy Dew. Peter Pears. B...
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