Turntable components - part 1
It must be as inert and rigid as possible so as not to transfer the vibrations directly stemming from the motor and drive spindle or indirectly by the sound pressure from the loudspeakers in the room to the tonearm and cartridge.
In most cases, for sound and cost-efficiency purposes, the plinth is made of MDF (PRO-JECT XPRESSION 3), though it can also be made of chipboard (REGA PLANAR 3) or multi-ply (AUDIONOTE). Some are a sandwich of various absorbing materials such as aluminium/MDF (VPI SCOUT MASTER) or acrylic/aluminium (WELL TEMPERED Amadeus GtA). Nowadays you can also find one-piece transparent methacrylate plinths (PRO-JECT 2Xperience). Besides its excellent acoustic properties, this material provides the turntable with a very stylish design. PRO-JECT also offers high end MDP and steel pellets plinths (RPM 9.2 and RPM 10 Evo, XTension).
Naturally, weight is also an anti-vibration solution. Therefore some turntables have a granite, marble, slate or stone plinth.
The plinth is uncoupled via different means: with plain rubber feet (3 or 4), metal, aluminium or composite cones, combinations of cones and sorbothane balls (2Xpression), squash balls (Well-Tempered), springs, etc. The feet can sometimes be very elaborate, like on the Pro-Ject Xtension, where they 'levitate' thanks to a clever magnetic repulsion system.
2. Sub platter
The sub platter is the part that supports the drive spindle well. In so-called 'rigid' platters it is built into the plinth and is usually made of the same material. However, it is often specific in suspended turntables (Thorens, Linn LP12, Systemdeck, Aryston, Heybrook TT2, Pro-ject 6,9…).
It can be made of steel, carbon (THORENS TD550), composite material, aluminium or of various alloys. In general, the sub platter is supported by three springs (compression system) or suspended by three springs (elongation system). Compliance (elasticity) varies from one manufacturer to the next, taking the structure's resonance frequency into account.
The size, weight, thickness and structure vary from one manufacturer to the next and according to the model. Its purpose is however always the same: the platter must be machined as perfectly as possible and spin true. Therefore is must be perfectly balanced, like the rim of a car wheel. Otherwise the spindle would wear prematurely and generate loud friction noise on playback.
Furthermore, the platter must resonate as little as possible and have maximum flywheel.
Some are made in MDF (REVOLVER, PRO-JECT Genie…), light alloy such as aluminium (LINN LP12, THORENS TD350), glass (REGA PLANAR 3, PRO-JECT 6,1…), ceramic (REGA PLANAR 9), and methacrylate (PRO-JECT Esprit, RPM 9 and 10, VPI SCOUT MASTER…), the latter option being quite clever, because this material has a resonance frequency very similar to that of a record and makes it possible to eliminate the platter mat. Its performance can be improved further still by adding a clamp (PRO-JECT RECORD PUCK, THORENS Stabilizer) whose purpose is to hold the record flat on the platter. On some highly sophisticated turntable models, the platter holds the record by suction (BASIS).
4. Platter mat
You have to use one with all alloy, glass and MDF platters. It wards off resonance from the record. Basically, they are made of synthetic rubber (Thorens TD166) or felt (LINN LP12, REGA PLANAR 3). Cork (PRO-JECT Cork it) and leather (PRO-JECT Leather it) yield excellent results. The platter mat's surface must be sufficiently adhesive so that the record won't slip. The platter mat is usually not necessary with acrylic platters. Note that when replacing a platter mat, you may have to adjust the tonearm height so as to make up for the difference in thickness with the initial model. It is therefore necessary to ensure that the turntable's tonearm is height-adjustable if the new platter mat is thicker.
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