To minimize vibrations from the motor and bearings of a turntable, it makes sense to eliminate the motor and bearings. There is already a magnetically-driven turntable in this establishment [link] and a maglev one on the market [link], but I haven't heard of one with an air film bearing before this one.

It works by having the platter float on a film of air generated by small nozzles built into the surface underneath the platter. The facing surfaces of the platter and the turntable's base are slightly conical to keep the platter centered. The platter's underside is also shaped with vanes to generate a torque about its vertical axis from the outward flow of air; the flow of air can be regulated to be able to play records of different rotational frequencies (with differential airflow between groups of nozzles at different radii, with the vanes also being radially limited, to preserve lift but vary torque).

Around the rim of the platter and the corresponding area on the base, there is a diffuser composed of specially shaped vanes and cavities, as well as a ring of foam. This absorbs the hissing noise of the air that supports the platter.

When the turntable is turned off (with an air valve rather than an electric switch), the platter slowly spins down and comes to rest in the base. No longer supported by air, it rests on rubber feet, which are shaped to aerodynamically blend into the vanes.

The compressed air can come from an air compressor in another room, or even another building, or you can use a nearly silent air compressor (widely available, but probably more expensive than a loud one) inside a soundproof box.

Piston-type air compressors probably typically don't produce a very clean pressure output—I expect it has a lot of noise, mostly from the pulsation of the pistons. Screw compressors are probably better, but still probably have some pulsation. Therefore, the turntable has air pressure low-pass filtering built in. This consists of a pressure regulator on the input, followed by a diaphragm pressure buffer tank, followed by a vane– flywheel inerter (which is also supported by an air film bearing). These are all made of audiophile-grade materials*, of course, as are the rest of the components.

A pneumatic amplifier/speaker unit [link] is also available, to use this turntable as a compressed air gramophone [link] to play music for a large audience or over loud background noises. Both apparati are also highly rugged, enabling use on remote job sites where compressed air is available from an engine- powered compressor, but electricity is not. In this case, you can use the special high-fidelity audio tube**, available separately, to connect directly from the turntable's needle to the speaker's comb valve, to eliminate all need for electricity.

*any old materials whose properties can be described in flowery language that makes them seem especially suited to low-noise, low-distortion audio playback applications

**a piece of narrow hydraulic hose with a braided metallic fabric sleeve

N/A [2019-09-28]
-- notexactly, Sep 28 2019

Magnetic coupling drive turntable by [hippo]. Mentioned in idea body [notexactly, Sep 28 2019]

MAG-LEV Audio ML1 Levitating Turntable https://www.audio-p...evitating-turntable
Mentioned in idea body [notexactly, Sep 28 2019]

Standalone compressed air speaker by me. Mentioned in idea body [notexactly, Sep 28 2019]

Wikipedia: Compressed air gramophone https://en.wikipedi...ssed_air_gramophone
Mentioned in idea body [notexactly, Sep 28 2019]

Spiral groove bearings https://en.wikipedi...iral_groove_bearing
WKTE [8th of 7, Sep 28 2019]

A simple plenum will equalize the flow from a piston compressor very efficiently; or two plena, with a diaphragm regulator between them.

But even a very large, low pressure air bearing will generate quite a lot of noise.

However ...

The field of tribology does offer a bit of hope. There exist "air" bearings that consist of two flat plates onto which are etched spiral patterns in opposing directions. When the plates are rotated against one another, air molecules are entrained and forced towards the centre, raising the pressure and reducing the friction to a very low level.
-- 8th of 7, Sep 28 2019


// A simple plenum will equalize the flow from a piston compressor very efficiently; or two plena, with a diaphragm regulator between them. //

Sure, but that's harder to sell to audiophiles.

// But even a very large, low pressure air bearing will generate quite a lot of noise. //

That's what the muffler ring is for.

// The field of tribology does offer a bit of hope. //

I've heard of rifle bearings in the context of computer fans, but never looked into their mechanism. How's that tribology, though? And adapting one to use as a motor would essentially make it the thing I described, though you could of course have a separate pneumatic motor, but that could have the same issues as an electric motor. Maybe a Tesla turbine would be good for that, though—no torque ripple, unless maybe from flow instability.
-- notexactly, Sep 28 2019



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