SP-10 Mat

I've been following this thread with interest because my latest project, an sp10mkII (early model) is in the works.
Here's a recent photo of the TT up inits plinth and doing its job.
http://www.theanalogdept.com/images/spp6_pics/User510/sp10mkII/Test%20Mule/TMbuild_31.jpg
and a link to the page where I document the entire process:
http://www.theanalogdept.com/user510_sp10_mkii.htm

At present I have the original mat on the unit. I was able to try out a BA mat 1 last Sunday. This was allowed when another sp10mkII owner brought over his BA mat1 for me to try out. I dealt with the obvious problem of the mat thickness being undersize for this TT. I placed a thin mat underneath the BA mat 1 and this resulted in a total mat thickness that was within a few thousandths of the oem mat thickness. this allowed me to hear the difference between my standard mat and the BA1.

Fwiw, I'm using a Graham 2.2 tonearm. And that allows a very convenient method for making adjustments to VTA/SRA on the fly. With that out of the way I can say that the BA mat definitely provided an overall improvement in comparison to the oem mat. The first thing I noticed was greater clarity in the upper frequencies. It might take me more time to fully evaluate the difference. But what I heard was enough to convince me that a solid graphite mat could be the ticket for this motor unit (and likely most others).

It is possible that the thin mat on the bottom may have improved "traction" between platter and mats.

The one negative I noticed about the BA-1 mat was that it was warped. When placed on a flat surface the BA-1 mat showed as much as 1/16th " of warp. And this was apparent as the mat was spinning on the platter. At one point I removed the underneath mat to allow the BA-1 mat to lie directly against the SP10 platter. Warp still the same and VTA was corrected via the Graham VTA adjustment facility. Roughly the same SQ. At least as near as I could tell during this brief listening review.

So my question now is; does anyone else have experience with a BA-1 carbon mat being warped? 2nd quetion would be; is it possible to straighten one of these mats without breaking it? I say this because I noticed that the mat is coated with some sort of polymer that (seems to) give(s) it a certain amount of flexibility.

Another thought to put out there:
Has anyone tried one of these players with a vacuum platter mat? I was thinking of the Vacuum mat produced by Thorens back in the 1980s. Now kind of rare, but interesting.

-Steve

Lew, on a side note, both a Krebs modified Sp10Mk3 and factory stock Sp10Mk3 reside here currently, although I personally have yet to directly compare at length.

Td, That's the first I have ever heard of a Boston Audio Mat being warped. Both my Mat1 and my Mat2 appear to the eye to be perfectly flat, and certainly there is no tell-tale sign of warpage when they are spinning. I trust your judgement, but be sure there is no other possible cause of your perception that yours is warped. If it IS warped, BA should take it back and exchange it for no cost, IMO.

One other thing: Why do you deem it to be so important to maintain the exact same thickness as the OEM rubber mat? A slight tweak of your VTA should take care of any minute difference between the BA and the OEM mats, and placing the rubber mat in between the BA and the bare platter will probably alter the sound, for good or ill.

Considering the materials of which they are made, I cannot imagine a BA mat warping post-manufacture. It could conceivably have been warped as a manufacture defect, I guess.

Chris, would love to know what you think of the two Mk3's, with vs without the Krebs' mods. (Of course, there are nothing but positive reports from other sources of which I am aware.)

Lew, thanks for your response.
re: mat thickness versus vta/sra. Plus one other factor; the sp10mkII platter has a pocket that a mat must fit within. And to be functional any mat would need to at least show proud of the platter rim. Just noting that part.

In any case vta/sra becomes a necessary adjustment when comparing one platter mat to another. And I keep a number of platter mats around handy just because I like to experiment with these items. Yes, the arm I'm using makes it convenient to adjust vta/sra. And I did make use of this feature during the comparison. But combine with with some earlier comments made to this thread about the BA mats.....that there might be some concern about the carbon mat losing traction against the platter under moments of higher stylus drag / speed corrections, etc. So, with the BA Mat One, its undersize thickness does allow the placement of a layer of "something" that could, conceivably improve traction between the carbon mat and the platter. Just a thought.

RE; BA Mat One and warpage.
1) I'd think that the solid graphite material, if left bare, may or may not be susceptible to warpage. Either during production or at a later date if improper mat storage became a factor. Just a guess. Why not check to see if solid graphite is or is not susceptible to warp.
2) These mats are coated by the mfr with a "proprietary" clear coat of some polymer material. I say polymer because I've held the mat and detected what I perceive to be a minimal flexibility to it. And I suspect that the mat prior to these coatings may not exhibit the same properties. and the coating will keep the graphite from shedding its graphite surface whenever it comes into light contact with.....anything. Graphite; very soft stuff that rubs off.

3) yes I'm certain that the sample I saw was indeed warped. As noted, ~1/16th inch. I observed this while allowing the mat to lay flat against a thick pane of glass that I keep around. and the glass I have proved to be very flat.

4) The mat does not belong to me. It was on a brief loan from another audiophile living in my area so that I could try it out on my SP10 mkII. And I liked what I heard. I'd probably look into a BA Mat 2 for this application. Also, I'm thinking about the benefits of gunmetal copper in this platter. I'm also thinking about any diy mat I may try in the meantime.

5) back to the clear coating that BA applies to these graphite mats. Perhaps during this process, when the coatings are applied and allowed to cure, it could conceivable be possible for the polymer to shrink while it cures / hardens. If applied unevenly.... Just conjecture.

But I did mention the warping I observed just to see if anyone else had seen a similar situation with one of these.

-Steve