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Completely flat platter/mat.

I am currently using a standard SL1210mk2 mat, then a felt mat that came with a Bowie box set and then another Techie mat that I rescued. This isn’t a magical acoustic sandwich though, merely a function of getting VTA correct with what I had to hand. I did try the felt on top too, not sure there was a significant difference apart from it sticking to the odd staticky new record which irritates me, hence the current configuration!

*after it failed several years later, from an old belt drive Techie that’d been part of a Technics separates system that had been traded in to SÖ and I’d bought for my little sister for the princely sum if £40! The amp and tape deck are still going strong though!)
 
Chops54 said:
hockman, is the Basis platter completely flat or does it have centre and edge relief?
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It's interesting that the platter is not completely flat. There is both center and edge relief so taking off a record is very easy. Further, I've found that the platter slightly slopes down from the spindle towards the edge/circumference. It is not a production fault, it's fairly consistent all round so it is part of the design. Not sure why it should be so though.
 
hockman said:
It's interesting that the platter is not completely flat. There is both center and edge relief so taking off a record is very easy. Further, I've found that the platter slightly slopes down from the spindle towards the edge/circumference. It is not a production fault, it's fairly consistent all round so it is part of the design. Not sure why it should be so though.
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The edge and centre relief will ensure that the whole of the record surface is in contact with the platter. If your Basis was designed to use a clamp that may explain the slight sloping of the platter. I would have expected it to slope the other way though. I'll have to do some reading up about Basis turntables.
 
I’d love to see some actual evidence of contact of a record on any hard surface regardless of contour. I’ve thought about this a bit since reading this thread and my bet is in 95% of cases the record will only contact the platter at a couple of points of less than a mm or so. The simple reality is records are not flat. Many are not even remotely close to being flat, but the ones that superficially look like they are (i.e. no massive dishing, edge warps etc) still are not flat. Go and grab what you think is your flattest record, play it and sit in front at an angle where you can see the arm bearing assembly reflected in the record surface as it plays. You will always see some ‘rippling’, ‘shimmering’ or worse in the reflected image as the record surface just isn’t flat.

I am prepared to bet you get far, far better actual contact area from a fairly thick felt mat that has a little compliance. The thing that got me thinking was the thread elsewhere about the old Rega Planet with is skeletal platter with three disks. I’m prepared to bet that gives more actual record contact and at more useful points than say a record sitting on a modern glass or copper mat. The Rega is at least supporting the record somewhere on each third of its surface. A hard and flat mat mat only be supporting a dished record either at the centre hole or at the extreme periphery.

Sure, one may be able to increase contact footprint with extremes like clamping at the label or periphery, but no way in hell would I let anyone play any of my vinyl on such a system! Just way too much risk of clamping a hard bit of dust into the playing surface (I’ve seen it done).
 
I agree with pretty much everything you said there Tony.

Going back to my original post and putting aside surface damage, warps etc, which do you think would be better purely for sound quality, complete contact of the record with the platter/mat or contact just at the label and outer edge?

Your comment about the Rega Planet made me think about the Hydraulic Refence turntable. Wylton has one of these?
 
Chops54 said:
Going back to my original post and putting aside surface damage, warps etc, which do you think would be better purely for sound quality, complete contact of the record with the platter/mat or contact just at the label and outer edge?
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I honestly don’t know. I don’t have any direct experience of hard mats as I’ve never put a record I owned on one. The hardest I’ve ever tried was a two-part Loricraft cork mat on the 301, but I thought the standard rubber one was no worse sound-wise and looked way, way better. In that case it isn’t only about record support as the rubber mat clearly damps the platter from ringing far better. That aside I’ve always used the mat the record deck came with. I do remember comparing a ‘Ring Mat’ on an LP12 with the stock felt one and thinking it sounded dreadful. It made the deck sound thin and gutless.

My suspicion is a three point support (like that old Rega) may actually be the best both for contact area and getting the contact even around the whole record. I’d say it was between that and a fairly soft felt mat. The three point support, assuming the label area was recessed, would certainly deal with dished records better than any other solution I can think of. It is a common pressing/manufacturing issue and I’m sure we all have many records that sit on the periphery on one side so look quite flat, but flip them over and there is a big rise and fall as they are lifted by the label area. A three point support would address that far better.
 
I use a felt mat on my AR XA turntable.
Acoustic Research fitted a soft ( foam ) mat originally.

Edgar Villchur knew what he was doing when he designed the XA.
It’s a turntable that, in some respects, has never been surpassed...
 
Chops54 said:
Your comment about the Rega Planet made me think about the Hydraulic Refence turntable. Wylton has one of these?
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Yes, indeed I do. Originally, I was going to use a solid mat with the Michell, but I soon realised that it sounds fine as it is. I have come around to the opinion that minimal contact is the way to go. I’ll get some pictures up in a while, but you'll see that the Spotmat has a similar contact pattern to the Michell. I just briefly tried the Spotmat against the two-part Loricraft cork mat, and I noted that the Spotmat seemed to give more air around the voice, a bit more depth and a bit more sparkle at the top. I don't think I've tried the Spotmat on the Linn; I haven't heard anything better than the felt mat on the LP12. The Spotmat is a foam construction btw. I use a glass mat on two of my turntables, but no way would I put a record directly on to that, for the reasons that Tony gave; one has a felt mat on it and the other a Spotmat.
 
Thanks for those replies and a lot of food for thought! I built the turntable in my main system using two Clearaudio platters, one stacked on top of the other. I’ve just realised if I turn the top platter upside down I’ll have a completely flat surface. I’m busy atm but tomorrow I’ll try it out both ways.

Yes let’s have some pics please Wylton.
 
Given the tracking force of the cart' is the only downwards force on a record during play, I think it is more than reasonable to assume that the cart' sees the record surface as rock solid.
So, what other consideration is there? Resonance of the "floating" bits of the record? If so, no two records will have the same "unflatness", so, no two should be similarly affected.

Depending on what material the platter/mat is, not touching it could easily be a blessing - no charge-up.
 
The more spots/areas provided for support, the lower the proportion that will actually touch the record. The only way you'd guarantee to get all to touch, would be to use two only.

Cheap and cheerful experiment - 3 very small sorbothane hemispheres.
 
Very nice Wylton. Your Hydraulic Ref is a beauty. I see what you’ve done with your Garrard and my good friend Dougie has a similar arrangement on his. We’re both in agreement that it sounds good.
 
I realised tat I had a small offcut of sorbothane sheet of near enough the same thickness as the felt mat on the LP12, so probably 3mm, so cut three roughly 10mm x 5mm pieces and am using them instead of the mat.

Give it a try, and see what you think.
 
Liking this bits of sorbothane and will be living with this for a while before going back to the felt mat to compare. For sure not a backwards move, musically or static.

Totally weird - a bare Linn platter excepting three tiny bits of sorbothane :confused:
 
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My preference has lately been towards flat hard surfaces to directly interface with te record, but I am sure my setup is fairly atypical.

The first two turntables I had precipitated the use of thick felt mats due to the nature of their design - the first one had a ringy stamped metal platter, and the second one had a platter machined out of MDF (I am still appalled by this). Both used a screw down clamp but the actual thickness of the mats allowed for a pretty good contact coverage throughout the surface of the record.

For the third (and last commercial) turntable I moved to an all acryllic platter which had a record weight and a label relief - I was glad to be rid of the mats because I felt that those mats caused more issues with playback due to dust retention and derived static than they helped with damping and record contact. Most my records are fairly flat and I had no real reason to concern myself with mats or the quality of the platter surface.

But when I built my current turntable, since the effort was mostly about research, I spent quite some time on researching proper platter contact. I had а very crude, but turns out effective method - I used very sensitive carbon paper between the platter surface and the record to see what is the possible pattern of platter-to-record contact. I made no record of those patterns (as I probably should have), but аs @Tony L rightly assumed, in most situations, platter to record contact (without clamping) is minimal and focused (in my "researched" cases) around the middle groove.

So I devised the following:

XLRzCx6.jpg


The top platter is machined out of Polyoxymethylene (Delrin is one of the trade names of POM), which is a much more pliable platter-to-record interface than pretty much any modern used platter material save for actual PVC for direct (no mat) contact. I machined a platter relief, but I also designed it to feature three supports (you can see two of them on the photo) which serve a double purpose - primarilly to support the top platter - but a secondary optional purpose is to support the record.

Using a screw-driver-like-tool, I can move the supports to either dive in the POM or to protrude slightly. This way, I can choose between having the record resting on only three points (the surface of each support is close to 1/4 inch square), or directly resting on the platter.

So I tried having:
  1. Record on three points, no "clamping";
  2. Record on three points, "clamping" via a extra wide (80mm diameter) record weight;
  3. Record on entire platter, no "clamping";
  4. Record on entire platter, "clamping" via a extra wide (80mm diameter) record weight.
In my experience, with that setup, the best results were achieved with option #4, which is what I've resigned to live with. One advantage of the POM also is the fact that it lends itself to cleaning very well, does not trap (or help embed in records) dust and is more eager to be micro-scratched than the record itself, which is a win. :)
 
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Tried a few mats a while ago and stuck with the felt mat that came with my Thorens TD550.

New cartridge and tried my old Lenco rubber mat. It hasn't left the platter.

Difference is a touch more focussed and clearer than the felt. The Acromat was just harsh although worked well on my old LP12.
 
Good post there InSides, thank you. My own turntable has stacked acrylic platters, the top one sits on six small cork pads placed 10mm in from the outer edge of the lower platter. The spindle extension is a push fit into the top platter so I'm unable to use a clamp.That will be rectified shortly. I've never used a weight having always preferred a clamp. Are there any benefits to using a weight instead of a clamp?

Bairnstorm, do you know which Lenco mat you use? I've had the best results with the GL78 mat. Seems to work well on every deck I've used it on. Very good at damping lively platters.
 
The primary reason for going for a weight instead of a clamp, for me, was due to convenience. Having used a clamp on two turntables, I often found the process tedious as I had to either press on the platter and/or record to be able to disengage the clamp (screw-down type).

Seeing I was able to design the bearing to my requirements I accounted for a heavy record weight and just went from there.
 
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