Thoughts On Turntable Clamps And Weights

@pindac  Suggest that you rest the record directly on the Delrin, as Delrin and vinyl couple very well (speed of sound is essentially the same). Also, you might do better with thinner Delrin, as thick pieces can be heterogenous.

Also, consider an air bearing. More trouble, but lots less noise. Best is air in all dimensions, like a thrust bushing from New Way.

Balancing is important, and easily done by machining an oversize cylinder. Thing is, it's easy to find an approximate centre of a cylindrical billet, so turn around that approximate centre, and shave off the excess to give you a perfect centre. Keep the cylinder on the lathe chuck and let it settle. Mark that point, and rotate it to the top. If it stays there, your cylinder is balanced. If not, remove a little material from the bottom, until the cylinder stays in any position. Then you have a static balance. 33 RPM is not enough to require a dynamic balance IMO.

This requires the lathe to have low stiction bearings. Also, be very careful to fit the spindle in the exact centre identified above. Repeat the balancing procedure with the spindle in place, if possible. This works with a massive platter. If the platter is light enough, go directly to turning and balancing on the spindle.

BUT - your machinist may have better ideas. It's his profession, after all, and I'n just an amateur.

I also got a 1mm cork mat to replace the felt.  If nothing else the dust and static problems are gone.  I tossed the felt and did not do a "with" and "without" test on them.

My LP turntable is a VPI TNT VI on a Townshend Seismic Sink (with super platter, VPI power controller, highly modified SME IV arm, Zesto Allesso SUT, etc). I tried VPI and an all copper exterior ring (latter used for a few very warped LPs) and VPI heavy center weight. They both negatively affected the sound with darkening the overall presentation. I play my LPs without a ring or center weight. I have heard on a higher end analog set-up a special wood many $1000s center weight that improved the sound. All my friends play LPs the same way, no rings or center weights. Same reason.  I think the platter is Delrin.  LP sounds neutral and dynamic just sitting on it.

@terry9 I have read your posts in the past and you show out as having a mind for the engineering side.

To get a idea of where my endeavours are going, the SP10 Thread on DIY Audio throughout the latter of last year and into this year covers a range of the platter designs to be used.

The designs for the bearing are coming from different places in Aus' and the UK, there is not as much work believed to be needed to create the measured run off's that are quite attractive.

I discovered the benefits of improving a generic type bearing design more that 20 years ago on a Garrard 401. Owned TT's since, that are in regular use, have all had a treatment in this area.

My interest in the Lenco GL 75 has enabled myself to meet quite a few who have done very successful work with this bearing type.

I am a vociferous advocate and encourager of carrying out this type of modification, meeting with a trusted support is the hurdle to be overcome.

My friend who has worked extensively on GL 75's, has gone to the extremes of having a Lenco Bearing Produced with a two part composite Spindle, Metal Spindle > Delrin Bushes in the New Machined bearing housing. The spindle to platter interface is using a material attached to the metal part of the spindle, where the material can be Natural, Thermoplastic, Metal or even a Composite.

When experiencing this in use as a Ebony Wood > Stacked Platter, the improvements was very very noticeable and quite outstanding as a functioning part when compared to other bearing modifications immediately available to try. 

This is a Spindle Mod', I am in discussion about for the alternative bearing design referred to earlier, Panzerholz would be my wood of choice. 

There is a more complicated bearing design in the making, I can't discuss it too much as it is not my work.

I have struggled to get a discussion going on a Air Bearing design. I have in my thoughts a design for one. I have to wait to see if it can be adopted into the design for this new complicated bearing design, seeing the dimensions of the New Bearing Housing and working with them, to offer the Air Bearing the optimised set up will be the challenge.                 

FWIW, Kenwood made a peripheral ring back in the early 80s for the L07D. If you use it, there’s a special setting on the power supply/motor control module so the servo then compensates for the added inertial mass. Yet the ring seems to slightly downgrade the SQ of the turntable. Darkens or closes in the sonics, slightly.