SLATE PLINTHS I recently started making slate turntable plinths or bases. I initially wanted a very heavy plinth for a newly acquired Thorens TD124 MK1, which came to me in the usual lightweight box plinth. There has been such a great deal of discussion on the merits of taking these vintage idler and even belt drive turntables and placing them in massive contrained layer damping (CLD) plinths that I won't labor the subject here. Vinyl Asylum seems to have daily threads on the subject. Virtually all plinths that people make utilize plywood and mdf. But I live next to a functioning slate quarry in a famous slate belt (the Mill's foundation is actually carved out of a bedrock of slate) so I thought, why not do this out of slate? Designing and fabricating these myself has allowed the incorporation of all the design elements I wanted in such a plinth: a. Great mass. Other companies have produced slate turntable plinths using thin sheets of slate, only 20mm or 30mm, and only one layer actually mates with the turntable motor unit. So damping is minimized unless the table is brought into contact with the whole mass of the plinth. b. No isolation of the tonearm mount. The armboard is in contact with the rest of the plinth, not vibrating at its own resonance. c. Easily removable, swappable armboards. You can switch tonearms in seconds. Just lift and remove.
Garrard 301
Pennsylvania slate is truly ideal, in that it is the softest slate of the commercial varieties found in the US, which gives it the best damping qualities. It's very, very heavy. Unlike other types of rock or stone, slate does not have a cryptocrystalline structure, but more closely resembles a fossilized book, or plywood with infinitely many layers, and much greater density. It is truly the perfect material to make a turntable base from- extremely well damped, hard enough but not too hard, dense, and, also, beautiful. Slate is a very beautiful material. Unlike other stone, slate is not polished, but "honed." After finishing to 1000 grit, it's oiled to give it a soft sheen and glow. This finish will last almost indefinitely, but if necessary, a wipe with an oil moistened cloth will renew it (natural boiled linseed oil, completely non toxic.)
Technics SP10
My slate plinths are thick, and usually made of two layers or pieces. Typically each layer is two inches thick, for a total of four inches. The slate is cut with a waterjet CNC machine (watch slideshow here), then finished entirely by hand. The weight can be nearly 100lbs for some models, but each piece is shipped separately, and is within UPS limits, at least for domestic shipping.
Thorens TD124
Plinths for the Thorens TD 124 can be configured as single or double layer. For clients ordering an OMA plinth we can offer as an option custom cut slate tonearm boards for any 9 inch tonearm. For those who wish to use two tonearms, or a longer, transcription type arm like the Schick (shown above) the single layer plinth is recommended. Weighing more than 70 pounds, this plinth comes with a tonearm mount that allows the new OMA tonearm board in slate or other materials to be used, ensuring proper tonearm height vis the elevated TD 124. With this style of arm mount, users have free reign to easily make their own arm base.
Armboards come in two basic styles. One is a modified rectangle-
And the other is circular, with the arm hole positioned slightly off center or eccentric-
The circular board allows you to change overhang by simply rotating the armboard. Either armboard requires the customer to provide the information about the desired tonearm to be used to custom waterjet cut the armboard. The removeable armboard design also allows customers to own additional armboards which can be setup with tonearms and switched out in less than a minute. Since the armboards are held in place by their own weight, with no additional fasteners, to change arms all one needs to do is remove the arm and slate armboard assembly as one piece. We can also supply armboards in solid hardwoods, or you can make them yourself. Cones can be used to support the plinth, or we can provide sets of three or four slate blocks in various dimensions as an optional extra.
Every plinth is completely custom made to your specifications. With our access to the quarry and waterjet cutting, we can make plinths for virtually any turntable, to any dimension. For example, if you wanted a six inch thick plinth with three tonearms, we can make it.
With our water jet capabilities, we can even carve your name in stone 2 inches thick.
Slate equipment racks are under development. Thanks to Steve Clarke from the Analog Dept. for his help with the TD124 prototype. He's written extensively on his experience with the plinth I made for his Thorens TD124. You can follow his thread here. Also credits go to David D'Imperio for his design assistance with the plinths. Photos © OMA