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LP12 stainless composite sub-platter

Discussion in 'd.i.y.' started by sq225917, Jan 7, 2017.

  1. sq225917

    sq225917 situation engineer

    I was in the pub last night with Mark, sampling the fine selection of strong dark ales that they have on tap and bottle and he mentioned that he'd been sent an LP12 sub-platter sample. The LP12 sub-platter and bearing shaft are pretty much the last unaltered piece on the modern LP12 and given the consistency with which they've produced them over the years it doesn't seem an obvious choice for changes. After all, heavy metal, check, polished and honed stainless steel shaft, check, mirror finished round bearing tip, check. What are you going to do to change this recipe, change the colour?

    As it turns out, 'change the colour' wasn't that bad of a guess, but there's a little more to it than just that. On returning to Mark's he handed me the sub-platter assembly and told me to go and play with it, so this morning I did just that.

    [​IMG]

    The sub-platter is actually a composite assembly, with a stainless steel bearing shaft, what I assume is a brass boss, which is pressed into and machined as one with the rest of the sub-platter, which is also stainless steel. The fit and machining is so good that to all intents and purposes, apart from the colour difference, it could just be one piece of metal. With a high standard of quality on the fit and finish I started measuring the bits that count. Straight off the bat you can feel some extra heft in the part and it's 100grams heavier than my old pre-cirkus part. The shaft is exactly 10mm, it's not 10.01mm or 9.99mm, the line on my micrometer sits exactly on the 0.0. The Linn part measures the same. To check the rest of the spec it needed fitting to my deck.

    [​IMG]

    Here's the thing though. I don't own an LP12. I actually run a Kuzma Stabi S 12", in which I've replaced the bearing, sub-platter and platter with LP12 parts. I don't like the look of the Kuzma platter, I'm not a huge fan of their Tufnol bearing and I have a completely different motor drive solution fitted to both the Kuzma and usual Linn options. The good news though, the LP12 bearing is a drop in swap and motor to bearing distance, bearing height, arm height and everything else and adjustable on my deck so i can compensate for anything in the set-up. My TT-psu is a digitally controlled, dual-mono, class A amp. Phase offset is adjustable in 0.01 degree steps to tune the drive to the motor's windings. Frequency is adjustable in 0.01hz steps and voltage for both phases of the motor drive are adjustable with trim pots. The whole thing is controlled by a USB to PC interface and I ended up with this solution after pretty exhaustively testing most of the commercial and DIY TT-psu solutions. AC or DC, analogue or digital, I've tested them and this set-up gives me the best speed accuracy and long term stability. After all, it's just a record player, all it needs to do is turn at 33 ⅓, right?

    [​IMG]

    The image above shows the control interface to my TT-psu, you can see I have the drive frequency set at 50.14hz, that gives me 33 ⅓. I use a 240 element strobe disc to check the speed and I look at it through a narrow slot in a plastic board. This removes any hand or head shake from the equation and ensures repeatability. I removed my sub-platter, fitted the new one with a couple of drops of silicon fluid into the bearing and set about measuring and resetting the speed. With the new assembly spinning away happily in place I had the reset the drive frequency to 50.22hz, as shown below.

    [​IMG]

    The difference between the 2 platters is 0.08hz. If that sounds like a big number, do the maths on the circumference of the sub-platter, it comes out at a couple of 100th's of a mm. That's great precision, really really great precision. Frankly it's probably as thick as the oxide layer that's built up on the side of my dull, finger print covered Linn sub-platter over the years. Vertically, the sub-platter sits just a midgie's dick higher than the original, less than a mm. Measurable, but not really worth mentioning.

    [​IMG]

    So, measuring the same, fitting the same and doing the same job, I wasn't expecting it to sound any different. My deck has no suspension, so the weight is inconsequential in terms of belt to plater height, there's no sub-chassis to drift, no apple cart to be upset. But upset I was. Upset that I've obviously been missing out. Where I thought I had arrived at my final deck solution with my last TT-psu upgrade, over a year ago, I now find that there's at least one more step in this particular journey. With the stainless composite sub-platter fitted there has a been a perceptible shift in balance. What I've often thought of as a slight hollowness in my deck's bass reproduction, a very subtle saddle and an associated bloom above this has gone. It's been smoothed over. Filled in. Erased. The new sub-platter gives a fuller more consistent and coherent bass presentation. Flourishes across Cello and Bass are better resolved, more even handed and precise. It has the same effect on phrasing with electric bass, making the playing sound more measured and more subtly accented when required. I swapped back and forth a few times and each time it was the same, better resolved and more considered with the new sub-platter. All of this leaves me in a bit of a quandary. I want one, I'd even go so far as saying that my deck 'needs' one. But I have absolutely no idea who makes them, or if they are even a production item yet.

    I thought I was done with turntable improvements, but apparently, all this time the icing has been missing from my turntable cake. Who knew?
     
  2. hp1

    hp1 pfm Member

    You mean the stamford audio cp12.
     
  3. Vinny

    Vinny pfm Member

    Slight mis-remembering there, HP1, but try this -

    http://www.ebay.co.uk/itm/Stamford-Audio-SSP12-Steel-Inner-Platter-embedded-Weight-SUPERB-Linn-LP12-NEW-/391617165525?hash=item5b2e33b8d5

    Strange that it is being sold as having "embedded weight" as its particular selling point. To add weight, it could be made of almost any metal and certainly would not need to be a composite of more than one metal, apart from the spindle, although in theory it could just as easily be machined from one piece of bar or a forging and the spindle alone induction hardened and ground - all very simple machining/metal-bashing processes..
     
  4. Patrick Dixon

    Patrick Dixon Imagineer

    Just give Mark your old one back and tell him you didn't like it. He'll never notice.
     
  5. YNWOAN

    YNWOAN 100% Analogue

    I think Stamford Audio are calling it the SSP12 (that's what it says in their eBay listing). However, I know very little about this design.

    Patrick, your cunning plan has been duly noted....
     
  6. TPA

    TPA Trade: Tiger Paw

    Hi Simon, it's produced by Edmund of Hercules/Mose fame. He sent two over to try out and so I sent one up to Mark as I thought he might be interested in trying it.

    I have been previously using one of Edmund's DC power supplies (Mober) and he had sent across an updated board and strobe which has significantly improved the way the motor gets up to speed (and maintains speed) LP12s sound fundamentally different with DC motors as Radikal owners will confirm. I've tried different DC set ups in the past and Edmund's Mober is the first I've tried that works properly.

    Anyway, back to the platter, yes it's an interesting development. I'm not entirely sure about the thinking behind it but it's clear that the change in materials appears to offer some benefits. The platter itself itself is also extremely well machined and very accurate.
     
  7. sq225917

    sq225917 situation engineer

    I've had another good listen to the modified lp12 sub platter this afternoon, lots of Agnes Obel. I really do like this very much. The differences are consistent from record to record and always in the favour of the upgraded lp12 subplatter.

    I'm not sure of the thinking behind the embedded brass, but the results are undeniable.
     
  8. YNWOAN

    YNWOAN 100% Analogue

    I've just been round to Simon's house and he was kind enough to A/B the difference between the standard and this 'upgraded' LP12 inner platter - there is certainly a clear difference between them! We also did some very unscientific experimentation which involved striking the two inner platters and also when coupled to the outer platter. The stainless steel and brass version rings strongly but cleanly and seems to have a quicker decay. The note of the Linn variant is flatter and seems to have a longer decay. When you add the outer platter there is still a ringing but it is damped and the decay is much shorter. How much relevance any of this is is another matter - I don't know.
     
  9. Vinny

    Vinny pfm Member

    Added mass is going to have two effects as a direct consequence of the increased mass/inertia - it will make for improved rotation speed stability (if there is room for such), and also affect the suspension characteristics in terms of bounce/oscillation. It would be interesting to do an A v B v C v D with this and the "uprated" springs and grommets that someone out there produces for the LP12.

    None of that gets at the 3 part construction logic though.
     
  10. YNWOAN

    YNWOAN 100% Analogue

    In terms of inertia the added mass will have a minimal effect as it is, a/ not that significant in terms of being heavier, and b/ not at the periphery but gathered at the centre of the platter.

    In the case of Simon's deck above there are no springs so that's not an issue.

    It's really more of a two part construction really as the standard Linn item also has a tool steel bearing shaft that is pressed into place, just as this design does.
     
  11. Vinny

    Vinny pfm Member

    The moment of inertia change is significant - irrespective of where the extra mass is, the centre of gravity of any and all platters must be very close to, ideally at, the centre of the spindle.

    I doubt that the fit is pressed - it is probably freeze-fitted, FWIW.

    It is also interesting that the density of steel and brass (and bronze) are as near as f*** it is to swearing, the same.
     
  12. YNWOAN

    YNWOAN 100% Analogue

    Well it depends what you consider significant to mean I suppose, but it really isn't. Where the extra mass is lockated is key to rotational inertia so not 'irrespective' of where the mass is located. All this is standard engineering theory so I'm really not sure why you are arguing this point.
     
  13. wylton

    wylton pfm Member

    So we're almost to the point where you can own an 'LP12' without any Linn parts in it.
     
  14. YNWOAN

    YNWOAN 100% Analogue

    Yes, only missing the outer bearing, outer platter, lid and hinges. When these exist you will be able to build an entire LP12 (sort off) from non Linn parts.
     
  15. Vinny

    Vinny pfm Member

    Changes in the moment of inertia depend on the % increase in the mass and position of the extra mass compared to the centre of gravity - neither of which we (or me at least), have. Obtain those and we can calculate the two figures......................

    Undoubtedly so, although arguably the major, most important component will always remain - the basic design principle. Whether that is good or bad................
     
  16. misterdog

    misterdog Not the canine kind

    Looks better in your images than their Ebay listing.


    [​IMG]
     
  17. sq225917

    sq225917 situation engineer

    It's 1300 vs 1200 grams, the outer platter is a couple of kg, so it real terms the extra rotational inertia is bugger all, maybe a couple of percent. In my deck the effect is reduced even more because the bearing is full of 3K silicon oil, so the spin down time from 33.3 without the belt is measured in seconds, as opposed to minutes with linn's standard oil. In contrast, the ringing modes are hugely different.

    I'd put the difference down to materials and transmission of noise characteristics as opposed to the slight difference in mass of the combined rotating elements.

    Putting a heavy record weight on makes nothing like the same difference.
     
  18. Dan K

    Dan K pfm Member

    Reckon that's it.

    I'm also surprised that nobody has started producing a DLC coated Cirkus yet. Add that to your list Simon, perhaps I could make a business out of producing them?

    Another idea. Has anyone put a PT Too bearing in an LP12? Now that you can get them made by true point, wouldn't that be the ultimate solution?
     
  19. andyr

    andyr Registered User

    That is extremely cool, Simon! I have a mate who moved on to a 'SkeletaLinn' before I did (different approach) and he has always said the Mazak that the Linn platter is made of ... has a sonic problem. (He is retired but fettles TTs for a business - so he knows how different TTs sound different.)

    So I want one of these ss sub-platters! :D So can you tell me:
    * where do I get one from?
    * do I need to buy a new Cirkus bearing to go with it?
    * is it better with a ss outer platter (do they make one)?


    Thanks,
    Andy
     
  20. YNWOAN

    YNWOAN 100% Analogue

    A/ I think in the U.K. (Which I know you are not so not a great deal of help) I believe Stamford Audio are the distributors. Wherever you can source a Hercules from will be able to get the inner platter.

    B/ No, you don't need to buy a new outer bearing.

    C/ I wondered the same but, at present, I'm not aware of a matching outer platter (I think increased mass really would be a problem for the suspension there.

    However, there is another Linn mod coming out shortly...
     

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