To join in on the discussion of alternate drive systems, I want to remind everyone that I have never written that one cannot obtain good results from a belt-drive, just that they are inherently inferior to the other two drive systems (once the bugs have been worked out), and that from an engineering point of view - that is engineering TO A PRICE, as engineering is meant to be - belt-drive is a failure as it requires a much larger investment to achieve idler-standards (assuming they can be achieved) than a sonically equivalent idler-wheel drive. I've often been on record praising the AR 'tables, Roksans, and such-like. For producing decent 'tables on a budget, the old platter/bearing, motor/elastic band solution can't be beat, nor profits, which is why they dominate/d (coming soon to a theater near you ;-)).
In this vein, I just picked up an irresistable belt-drive: a very rare "Unity 1 Rotary PLatofrm", which is as impressive as it sounds. It sports a solid brass platter, with most of the mass concentrated on the rim, which weighs in at 15 pounds! Worth its weight in gold. It is fixed to a truly superb main bearing, made of a sort of steel of extreme hardness, as neither it nor the bushings show any sign of wear whatsoever. Something is laser-imprinted into the metal of the shaft. Other than that, it is a classic belt-drive with a motor and belt. Story is it was manufactured in the '80s, was too expensive to manufacture (brass alone worth its weight in gold) and so carried a higher price-tag than people were willing to swallow, and the fellow went bankrupt. But, some day when I'm done with other experiments, I'll rebuild it into a plinth, polish up that brass, have an acrylic mat made, and set it up with a tonearm. It'll be fun, and hopefully musical!
There are all sorts of problems with slate - marriage of surfaces - Lenco-to-slate (regardless of the CLD nature of slate, it is still stone and so hard, which means metal slapping against stone as no surface is perfect) and slate-to-plinth - the inability to Direct Couple, not to mention the long list of perils listed by Mosin and so on - but I'll give it a go when I have time (still working on Reinderspeter's top-plate). The traditional recipe, i.e. wood, still represents the best real-world solution, and though this requires quite a large platform, the Direct Coupling absorbs the noise away from the 'table AND the vinyl (magically ;-)) to excavate the mighty Lenco/Idler and DD and even belt-drive potential. One gets used to the size: way back when I built the Canadian Rustic I thought it was huge (now seems quite puny), then came the Giant Lenco which now in the context of an even larger plinth (and certain humongous belt-drives) looks just reasonable, and now I have the Ultra Lenco which now seems just normal. Of course, carrying it is a bitch, but I wouldn't want to sling a Walker into my car either!!
I hooked up a pristine H-K Citation Twelve Deluxe (powerful vintage dual-mono SS amplifier) to my Yamaha NS-690s, hooked THAT up to my Ultra Lenco/restored main bearing, fired up Nine Inch Nails "Pretty Hate Machine" and thought I was being hit by an earthquake (I rushed to the volume control) the house shook so hard!! The dog ran for cover. Astonishing how much powerful and DEEP bass (like fleets of submarines sailing at depth among depth charges in my living room) the Lenco can force smaller speakers (the Yamahas are average-sized 3-way stand-mounters) to produce!! Meanwhile, all the itty-bitty details continue to remain clear above it all.
Anyway, have fun all, more to report soon-ish!