Preface
A technical specification describes
what technical goals are to be achieved by a device and it does so structured and in detail. It should not prescribe methods
how particualar problems are to be solved. Exceptions from that rule should be rare if present and necessary from an entirety perspective.
General
- the turntable should preferably use only materials that are reasonably easy and universal to obtain within a resonable lead time. For the case two equivalent materials for the purpose exist, the material that is are reasonably easy and universal to obtain within a resonable lead time must be preferred.
- use of special and hard-to-obtain tools and manufacturing techniques should be restricted to an unavoidable minimum. Tooling and manufacturing techniques should be within easy reach of everybody.
- everything in connection to the design of the turntable shall be made available in a format usable to anyone wanting to make the design so no application specific fileformats but formats like .dxf, .gif, .jpg, .txt so that anyone using any OS, computer can handle the data. Format .bmp is to be avoided if possible, due to unnecessary big file size.
Physical requirements, Turntable
- a TT should be as immune as possible to any sort of mechanical resonances and partial oscillations.
- primary purpose of a TT and its tonearm is to let the phono cartridge stylus move undisturbed and only as guided by the record groove. The cartridge shall be kept quiet and not any other movements caused by TT or tonearm should be overlaid to the groove-caused stylus movement.
- Particularly oscillations coming from the floor the TT is standing on should be prevented from reaching cartridge and tonearm.
- the TT's platter should rotate around the bearing centerline at constant speed and wihtout any other rotational or translational movements overlaid. No tilt, nutation, precession should be allowed.
- for the case that motor and platter are separate units: rotational masses of platter and motor should not execute rotational oscillations; they should not be able to mutually exchange rotational energy.
- a high rotational inertia of the platter is desirable to keep platter speed statically and dynamically constant.
Technical necessities, derived from reqiurements above
- Choice of auxiliary energy is not limited to electric energy. However, all usual safety rules have to be kept for the chosen form of auxiliary energy.
- All mechanical components should be stiff by shape in order to minimize partial oscillations.
- Materials and material compounds should be chosen it minimize discrete component resonances and partial oscialltions and to decrease resonance as far as possible
- the TT shall have means to decouple motions and oscillations of the floor. If the decoupling means work by overcritical damping, then their resonace Q should be as high as possible and the resonance frequency should be as low as as possible, 1 Hz or below wold be desirable. The decoupling construction shall strive to oscillate in vertical translation direction only, like a piston. It should strive to redirect horzontally tranlational and any rotational oscillations to the vertical translation oscillation within few oscillation periods.The decoupling contruction shall support easy and precise levelling.
- If possible, the record, particularly the proximity of the stylus, should be able to transfer its partial oscillations to the platter.
- It is desirable to provide firm mechanical contact between record and platter in order to prevent movements of the record relative to the platter.
- The platter's bearing should not generate any mechanical noise. It should provide axial and radial deviation as close to zero as possible.
- The element connecting motor and platter and transferring enregy from motor to platter should not be able to store energy itself; it should not be elastic.
- The motor should be as free from speed ripple and torque ripple as possible. Motor control/supply should providea speed regiulation in order to prevent speed drift.
- Final control elements should be easy to access. Control elements influencing more than one parameter only are forbidden.
- Installation and de-installation of the TT and its components must be possbile without component destruction.
- Components and assemblies sensitive to wear and to sonics shall be exchangeable without dismantling or de-installing the whole TT.
- The TT should not have any sharp edges, corners, chamfers for protection of records. Records accidentally slipped out of the hand of the user deserve to have a chance to survive.
- the TT should allow technical means cancelling record (side) excentricity.
Dimensions and compatibility requirements
- Platter diameter: max 320mm
- Height distance platter surface to tonearm mounting platform top surface: min 35mm
- Playback speeds from (16?) 30 to 120 rpm as fixed speeds with a variable part or with an easy and repeatable means of setting.
- Platter acceleration should not exceed 30 seconds.
- Electronics used should not depend on the voltage/frequency of the line power.
- A wide variety of tonearms should be supported; this includes 12" pivoted tonearms and linear tracking tonearms as well. If the tonearm requires a plinth or larger mounting surface, the tonearm platform interface must allow to mount a platform big enough and stiff enough.
