Turntable (SME) musings

[YNWaN]

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.

[hifi_dave]

Come back....... you can't leave us hanging on like that...:eyebrows:

[chris@panteg]

:scratch: mmmm interesting ?

[YNWaN]

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....

[Beobloke]

..........(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.

[DSJR]

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.

[hifi_dave]

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.

[DSJR]

Ah, but it aint a Techie Dave, it aint a Techie....... and the SME is ten times the price as one when bought new...

[YNWaN]

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.

[pure sound]

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.

[YNWaN]

I refer you to the first sentence of post #9. If you choose to read a level of criticism into what I have written then that is your prerogative - from my perspective I am describing a particular situation in a particular circumstance. The point is not really about SME (for me) but to highlight how sensitive turntables can be to apparently minor setup issues.


I was never aware of any pitch stability issues or problems with structure borne feedback.

Well good for you; however, SME themselves have gone to considerable further effort to address structure borne feedback issues in the 20 and 30 (so presumably they don't entirely share your view or there would be no point in addressing this issue further).

[Stratmangler]

Well good for you; however, SME themselves have gone to considerable further effort to address structure borne feedback issues in the 20 and 30 (so presumably they don't entirely share your view or there would be no point in addressing this issue further).

And in what order were the SME turntable models introduced ?
It seems to me that SME have gone from making extreme effort to addressing structurally borne feedback issues, to not addressing them to the anything like the same degree, almost as though it were an irrelevence.

[pure sound]

I'd say it was no more prone to structure borne feedback than any other unsprung deck might be. Like the Kuzma Stabi, a Rega or probably a NAS it will work well on a sensible platform and perhaps best on a wall shelf. The Models 20 & 30 are of course significantly more sophisticated and cost a good deal more aswell. I don't know anyone who'd suggest that the Model 10 is as well isolated or as good sounding as either. I suspect SME's view would be that they have made tolerable compromises to get it to the price it sells for.

With regard to the deck you've been looking at, I was surprised to hear of a flat on the ball but more surprised to read that it was replaced with a ceramic one. Given the results people appear to have been getting with a ceramic ball in the Garrard bearing, it seems a surprising choice.

[hifi_dave]

And in what order were the SME turntable models introduced ?
It seems to me that SME have gone from making extreme effort to addressing structurally borne feedback issues, to not addressing them to the anything like the same degree, almost as though it were an irrelevence.

As I recall - 30, 20 and then 10.

I guess they feel that they can't provide such a sophisticated suspension at the price. You have to get something extra by paying more !!!

[YNWaN]

Isolation is not an irrelevance - though some would like to believe otherwise. As Dave writes above, the 30 came first - then the 20 (which is a simplified 30) and then the 10 (which is quite a bit more simplified than the 20 (it's also quite a lot cheaper though). All three models are still produced and each subsequent model was designed as a less sophisticated, but cheaper, solution.

I see that the thread has already become a political axe grinding opportunity so I will leave it there.

For the record, I have no issue with SME - interesting designs, well engineered and nicely finished. The issues reported earlier related to poor adjustment (or care) by some earlier owner - hardly SME's fault.

[pure sound]

I see that the thread has already become a political axe grinding opportunity



Has it? Where?

It could've been worse. Someone might have started whingeing about the price of the box ;)