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Thread: Turntable (SME) musings

  1. #1
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    Default Turntable (SME) musings

    Someone I know has recently bought an SME10 and I have had the opportunity to observe it completely taken to pieces and investigate it closely.

    Now this item was purchased second hand and my friend wanted to make sure that everything was in proper working order. In particular he was eager to check that the speed was consistent.

    Gotta go - more to come.
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  2. #2
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    Come back....... you can't leave us hanging on like that...

  3. #3
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    mmmm interesting ?
    Chris

    We've gone on holiday by mistake !

  4. #4
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    Humph..sorry chaps - back now (I didn't expect anyone to respond as I haven't really written anything).

    Anyway, a reasonably cursory check of the speed with a strobe suggested that it was both slightly fast and not desperately stable - every third rotation (approx) it would speed up a bit. So we took the whole thing to bits for a bit of an inspection. The first interesting feature is that the bearings main shaft is actually a cone (i.e. wider at the top than the bottom). A fine screw in the base of the bearing allows one to adjust the height of the thrust pad so that the pressure that the two parts of the bearing mate at can be adjusted. Obviously, very tiny adjustments to this parameter make huge changes to the friction levels of the bearing. However, even after careful adjustment the speed instability issue remained. The second thing we noticed that the 10 has the AC motor mounted really very compliantly (more on this later) and the motor had become tilted towards the deck (some manual adjustment corrected this) - still the speed instability remained. Inspection of the shaft of the main bearing revealed that what looked like a hair was stuck to the shaft. In addition, the belt runs in a groove in the sub platter (with shoulders) and the motor pulley also has shoulders. By the look of it the belt (quite a tight, low compliance, design) had been running against these shoulders and had worn a bit. By this point the finger of blame was pointing at the SME's power supply but after the bearing hair had been removed, and the belt replaced, the speed stability issue was cured (the speed was still slightly fast but that is because the gearing is not absolutely spot on). One other thing I forgot to mention was that the ball bearing that the end of the shaft bears upon was found to have a small, but clearly discernable, flat spot on it. To be honest this was hardly surprising as something has to wear. The two parts of this type of bearing cannot be identical hardness’s – either the end of the shaft is wearing or the ball (thrust pad) is. This problem was easily cured by rotating the ball a bit. I have come across people using ceramic balls for bearing shafts to run against. Inevitably these are extremelly hard and do create wear at the end of the shaft.

    I was interested to investigate the SME’s suspension and had a close look at this. Reviews of the 10 described it as have a synthetic polymer suspension (like Sorbothane). However, I was very surprised to find how stiff this suspension was (almost zero compliancy both vertically and horizontally). Closer inspection showed that the polymer bush is actually very soft but the construction method altered the compliancy enormously. The bush is entirely entrapped within a metal cylinder (no sideways movement possible) and a steel shaft runs tightly through the middle. Because the bush is so tightly held it has very little opportunity to distort or expand – as a result it is effectively rendered less compliant. A metal washer rests against the base of the bushing and altering the diameter of this washer will effectively alter how stiff the vertical element of the suspension is.

    To be honest, I was very surprised by this element of the design. By constructing the suspension elements in this manner the isolation properties are significantly reduced (negligible in fact) - in comparison, the feet that the whole deck sits on are very much more compliant and provide the majority of isolation. Perhaps this element was chosen to counter the fact that the motor is much more compliantly mounted (to reduce noise transference). However, I would personally do it the other way round and have the motor rigidly mounted and the chassis more compliantly mounted (interesting that SME chose differently though). Effectively the SME is a completely rigid design – not quite as much as a NA Dais for example – but much more so than a Roksan which also uses polymer bushes for isolation.

    Sorry, it's not the most exciting story this - no wonder I don't start many threads....
    Last edited by YNWaN; 27-04-2010 at 10:30.
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  5. #5
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    Quote Originally Posted by YNWaN View Post
    ..........(the speed was still slightly fast but that is because the gearing is not absolutely spot on)......
    If it's a later deck, the speed is adjustable.
    Engineers: fixing problems you didn't know you had in ways you don't understand.

  6. #6
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    Interesting that SME seem to have made rods for their own backs with this one (I'm sure it doesn't need to be as complex as it is). The one we had in 2003 or so sounded very good indeed and didn't seem to have any speed issues tbh.

    I still think that decks like this are priced for cachet rather than performance. I mean, a Dias should run at the right speed, the belt doesn't usually deform or stretch over the years and it's as near to fit-and-forget as I could imagine.
    Tear down these walls; Cut the ties that held me
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  7. #7
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    In thirty years of selling Nottingham Analogue turntables, I have never had one which needed a replacement belt. I have sold a few belts to people who wanted a 'spare' but never had one which needed a new belt.

  8. #8
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    Ah, but it aint a Techie Dave, it aint a Techie....... and the SME is ten times the price as one when bought new...
    Tear down these walls; Cut the ties that held me
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  9. #9
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    Quote Originally Posted by DSJR View Post
    Interesting that SME seem to have made rods for their own backs with this one (I'm sure it doesn't need to be as complex as it is). The one we had in 2003 or so sounded very good indeed and didn't seem to have any speed issues tbh.

    I still think that decks like this are priced for cachet rather than performance. I mean, a Dias should run at the right speed, the belt doesn't usually deform or stretch over the years and it's as near to fit-and-forget as I could imagine.
    I'm sure that speed issues are not inherent to this design - I was more interested in why they existed in this specific circumstance (apparently minor issues working together). The SME10 is not a complex construction as such. However, the main chassis suspension is so stiff as to be essentially redundant and certainly this aspect could have been realised in a simpler way (although it still does not consist of many components). It is nicely made and finished - such qualities do not come cheap.
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  10. #10
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    I've heard the Model 10 sound satisfying on many occasions often with quite prosaic mm cartridges fitted. I was never aware of any pitch stability issues or problems with structure borne feedback. It's a simple, well executed fit 'n forget design that gives the lie to the idea that belt driven turntables can't sound stable, solid and energetic. A deck you could install for your mother & not have to worry about.

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