Vintage DD turntables. Are we living dangerously?

Lewm - Is there anyone here who adheres to the notion of elevating the LP in space....

Lewm - My tonearm and platter are already "in space"
I also preferred my records firmly grounded in between. Later in personal conversations with Verdier (prior to his recent passing-RIP) he confirmed to me that his TT was designed to be used with no mat.

Halcro
I've also got a glass mat on its way from Japan.
Apparently Victor produced one for their turntables and get this.....the instructions say that the pigskin mat is designed to go UNDER the glass mat...
This would never have occurred to me...
Of course I'll try it both ways....but I wonder if you've tried a suede mat UNDER your Achromat..
Worth a try....those Victor engineers knew their 'onions'....

I have heard of "pheasant under glass" but never pig. Analog can be so much fun......

Dave, How much does the Resomat weigh, in comparison to the stainless steel platter sheet on the L07D? One of my reasons for not experimenting with the L07D, besides the fact that I adore its sound already, is the fact that the mass of the platter sheet is figured into its servo design. If I were to sub out the platter sheet, I'd look for something of very similar mass.

03-16-15: Banquo363
One thing for certain is I don't know the first thing about motor oils. Here is what is available from Redline (from their website) as far as their race oils go:

20WT Race Oil (5W20)
30WT Race Oil (10W30)
40WT Race Oil (15W40)
50WT Race Oil (15W50)

And here is what RP offers in their XPR line (the line Doron recmmended to me):

XPR 3.1 0W-5
XPR 0W-10
XPR 5W-20
XPR 5W-30
XPR 10W-40
XPR 20W-50

@ the Redline, RP guys on this thread (Banquo, Doron, Lewm, others...)

Re: the bearing well lubricant discussions...

Recently read the synthetic fluid postings here. Found it ironic as my son just bought a used sports car and sent me a bunch of url's to review. they discuss RP and RL as well.

like this one

ok, nothing to do with this thread, but the similarities are striking. These guys changing out mineral fluids for synthetic in the gearboxes; sort of like you guys with the thrust pad wells ? Anyway you guys reminded me of them.

For SP10MKII owners with worn out thrust pad wells.

You can get some here

Happy listening

Fleib,
I don't think the record/platter interface is understood as you claim and that's where we differ...
If it were....there would not be the plethora of platter materials, shapes and weights nor the cornucopia of platter mats (materials, thicknesses etc).
I don't believe there are even two turntable manufactures with identical platter/mat combinations...?
And if...as you declare....

The purpose of a mat is to provide a stable surface with a similar impedance of the record,

then the majority of turntable and mat manufacturers fail in this endeavour..😱

Some think the best mats are forms of acrylic, methacrylate (Delrin), carbon, or vinyl.

And some people DON'T think that....
Some people even think that NO mat is better....and on some platters I have found this to be true...
And then, as Lewm points out....some even think that the less contact the record has with a platter...the better😊

If you believe that all these opinions reflect an "understanding" of the record/platter interface....I simply beg to differ...😎

Dgarretson, although I've not seen a PD444 in pieces, probably its bearing spindle sides were cut into a shape resembling a helical gear. When the spindle turns, such a gear thread will exert a pumping action on the oil contained in the bearing housing. This pumping pressure will center the spindle (so that a hydraulic film is maintained between spindle and bearing housing), and partially unload the spindle pressure on the thrust-plate (depending on the orientation of the helical cut).

With this kind of internal structure, it would be no great surprise for the bearing to be sealed.

Other turntables incorporated a similar "Archimedes pump" philosophy. For example, Trio-Kenwood's "DL" motor (employed in the KP-880 and later models) had a herring-bone pattern cut into the spindle sides, again for the purpose of pressurizing the oil inside the bearing housing and centering the spindle.

As to why the magnetic route wasn't pursued, for sonic reasons most likely Luxman didn't want full platter levitation, which meant that simpler hydraulic partial levitation was sufficient to protect the thrust-plate from the weight of the platter that they chose to use.

kind regards, jonathan