VPI HW-19 Mark III
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Opus88, if your objective is to ensure excellent connnecton of LP to platter and flattening of the LP on the platter, a screw-on clamp is not the only solution. My Walker Audio Proscenium turntable uses a smooth spindle and yet has among the most effective record clamping of any turntable out there. The secret is in the design of the clamp, not whether the spindle is threaded or smooth.
For me, I would avoid using screw on record clamp at all cost. The reason is that the spindle is usually an extension of the bearing shaft with has direct contact to the ball bearing/thrust pad....If using a screw on record clamp on the TT, the grinding noise from the ball bearing/thrust pad will transmit throught the bearing shaft to the spindle then to the clamp, LP and noise will be pick-up by the cartridge. The 'screw on record clamp' is not well thought design. A record weight or damper is a better choice.
For those who've asked for some further details, the Walker Audio clamp uses an internal Delrin bushing. (I've not seen the Basis design, which may be similar.) The bushing fits inside the clamp via threads on the outside of the bushing, but it is smooth on the inside and slides over the smooth unthreaded spindle. As one tightens the clamp, the bushing is pulled up into the clamp forcing it to compress around the smooth spindle. As the bushing tightens onto the spindle, the clamp's outer circumference is pulled down onto the surface of the LP, flattening the LP against the platter. With this configuration, as much pressure can be applied against the outer circumference of the record label as any threaded spindle clamping arrangement. As with any clamp, some judgement is required for how tight to pull everything together. The clamp is as rapid to apply and remove and it works as a single integrated unit. The clamp also is quite heavy, being a massive unit of machined brass.
Edle, you raise a good theoretical objection to clamps that attach to the spindle. In my listening with VPI, SME, Walker Audio and other turntables that use this approach, I can't say that I've ever actually heard the downside you postulate.
You raise a valid point, but as usual it's all about implementation. The design and build quality of the bearing will have a major impact on the costs vs. benefits of a screw-on clamp.
On my old HK/Rabco ST-7, bearing noise and intra-plinth vibration levels are so high that any record clamp, even a light weight Michell, seriously degrades the sound. The spindle isn't threaded but if it were I suspect the table could be the poster child for your theory: it would probably go from noisy to unlistenable. ;-)
OTOH, all Teres tables include a screw-on clamp (there's another one for Opus88's list). The bearing design and BQ are such that clamping the record firmly makes a significant sonic improvement, and there is no noise that can be attributed to bearing friction. The table is effectively free of bearing noise and silent grooves are exactly that, even with the gain controls turned well above safe listening levels.
Assuming a well made bearing, intra-vinyl resonances from stylus/groove friction are VASTLY greater than bearing noise. Clamping to a massive bearing can provide an effective pathway to evacuate and eventually damp certain frequencies, to the betterment of the sound.
A record weight or damper may or may not perform better, again depending on implementation, but IME bearing noise is not necessarily a reason to avoid threaded clamps. The devil's in the details, as usual.
IME a center weight or clamp won't do much for a bad pinch warp. Dish warps can often be flattened, even when playing the concave side, but pinch warps require a vacuum platter or periphery ring.
In truth, if one's arm and cartridge are reasonably good trackers, warp-flattening is not the main reason to use a hold-down device. The main benefit of weights, clamps, periphery rings and (I suspect) vacuum hold-down is to provide evacuation paths for and dampening of intra-vinyl resonances.
The drop in noise floor and improved low level detail and clarity from weights, clamps and rings is much more audible than any flattening of the record - at least IME.
Add the Kuzma Stabi to those tables with threaded clamps.
Edle, if your theory of vibration transmission with threaded clamps is true (and it may be per Dougdeacon's observation), why would it not also apply to clamps which grip the spindle in some fashion to secure hold down? To be effective on a smooth spindle, this must be a tight grip and that would still promote transmission if I have any understanding of physics. The only way around this would be a heavy weight which would not need a tight coupling, and that might introduce micro chatter.