There’s a reason why serious turntable manufacturers take great care in precision of manufacturing heavy platters. To fight vibration. Holbo has a 5kg aluminum platter. Use a good quality precision manufactured record clamp and couple the record directly to platter.
Use acrylic mats as dust cover. That’s about what they’re good for
I agree that in general, the record should be in firm contact with the platter. But there are some fine considerations!
Hard to know where to start on this one! Garrard was a serious manufacturer in its day, and had a fairly heavy aluminium platter which was die cast, machined to the standards of the day, and finally balanced by drilling small holes. The platter was designed to be easily removed, being seated on the bearing using a Morse taper. If it did not lift straight off, you we told to use a block of wood to tap it loose with your third hand.
Like most metal objects, the Garrard platter rings like a bell so it was supplied with a rubber mat. I still have the original mat but it is a bit ragged round the spindle. Now that SME has bought all things Garrard, and is manufacturing new old stock 301s, they have been able to precisely reproduce the mat. However, they will only supply it with their ’new’ 301s which are of course stupendously expensive! I’ve seen prices around US$40,000.
What about vibrations emanating from the stylus? I don’t think anybody in the 1960s thought very much about vibrations from the stylus being propagated through the vinyl and reflected back into the stylus, ready to be re-amplified. But this is a focus for many designers these days. The first requirement is a good impedance match between the vinyl record and what it sits on, so vibrations flow into the substrate rather than reflect back. Acrylic is a very close match and is used for platters by several manufacturers, including cost-no-object Wilson Benesch.
The Funk Firm Acromat line is made of very stiff acrylic full of tiny bubbles designed to absorb vibration. I bought a 5-mm thick one for the Garrard - and adjusted the tone arm height to suit.
The Holbo arrived later. You are correct, it is not supplied with a mat, and the Delrin spindle is short. One of the reviews states that its platter is made of Delrin, which is an easy mistake to make because because the surface is so smooth and black. But Holbo says it is aluminium and anodised. I gradually noticed when playing records on the Holbo that they seemed to pick up clicks (static?) faster than when played on the Garrard / Achromat combination. I moved the 5-mm Achromat across, but the spindle was too short to reliably centre a record and the hefty Holbo puck (630-grams).
I don’t know why a metal platter should increase static. Anodising can produce a thick layer of oxide on the surface, potentially 150 microns thick, which would act as an insulator
So I bought a 3-mm Achromat for the Holbo which coincidentally arrived in the same timeframe as the DS Audio cartridge. Here I broke a good rule of science. I made two changes at the same time!
Now the Achromat came with instructions to stick it to the platter, using six tabs of extremely thin double-sided tape. I had got into the habit of helping the Holbo come to a stop by slowing the puck with my fingers. With the Achromat, this could cause slippage, so I reluctantly stuck it down with the tabs. So now it is no longer a matter of seconds to remove it.
The Achromat has a depressed central area to accommodate record labels. The Holbo puck has a recess at its bottom to concentrate down force close to the edge of the label. So short of a vacuum, I think the record and the platter are pretty well coupled.
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