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In Reply to: RE: right. posted by user510 on April 25, 2017 at 18:21:01
I guess it's the main bearing that's the problem then. Because it definitely flexes back and forth a lot. Loose machining of the bearing and spindle. Still a bad design....
Follow Ups:
"I guess it's the main bearing that's the problem then. Because it definitely flexes back and forth a lot. Loose machining of the bearing and spindle. Still a bad design...."
The design looks ok to me. If there is a problem with the platter bearing then there is a problem with 'execution' of that design. Perhaps a manufacturing defect?
-Steve
Looks like the motor is stationary and not mounted to move in unison with the bearing/platter/tonearm. If so, I would view that as a "problem", because if the suspension bounces, the belt is stretched between the moving platter and the stationary motor. This causes speed instability. Again, perhaps I do not understand the construction.
And I keep thinking that Audiosoul is telling us that the bearing in his unit can move independently of the tonearm mount. Which ain't good either.
This design is consistent with most previous suspended subchassis architectures. The goal is isolation of the platter/tonearm from motor vibes. In practice it works well.The subchassis does not normally bounce around during playback. Unless there is a disturbance such as footfall on a flimsy floor or other seismic events.
See all the many postings re: AR/Linn/Thorens with regard to footfall.
This design, likely because of its use of elastomer pucks in place of springs, will be less susceptible to footfall and other seismic events.
There is no problem with the design. It is time tested and well proven. In reality, there are those that just don't like it.
-Steve
Edits: 04/27/17
My main point was that having a stationary motor and a platter that can move independently of it due to environmental disturbance could cause a problem with speed stability. I yield to John on his point that most suspended belt-drive tables are built that way.
At the very beginning of this exchange, I was also wondering whether the OP is telling us that in his turntable, the platter can move independent of the tonearm mount. Which is really not good, no matter how you slice it.
however the op kept saying that it was a design problem. And my answer to that is that, whether we 'like' the design or not, it is a well established design --even if-- the platter can change position relative to the motor.
One of the tricks to getting the suspended sub-chassis type player working at its best has to do with adjusting the suspension so that the bounce is as close to being straight up/down vertical as is possible. When one of these exhibits a sideways jiggle, sonics tend to go lack-luster. And on and on, etc.
But yes you're right, the design has inherent flaws which detract from absolute control over wow/flutter.
Perhaps I've been less than generous in my replies simply because this subject has been discussed so many times and in depth.
The op did suggest that he saw some sideways motion of the platter and pointed to possible problems with the platter bearing. However none of us can see what he's seeing and I don't really trust his discription.
-Steve
> Again, perhaps I do not understand the construction.
That would be my guess since every suspended turntable I've ever seen has its motor mounted on its stationary plinth while its platter and tonearm are mounted on a suspended chassis. This is done to isolate motor noise from the LP and cartridge.
When a turntable is playing, its suspended chassis should not be bouncing. If it is, you have serious problems.
Good luck,
John Elison
presuppose that the suspended elements are intentionally free to move independently of the support structure? Although the motion may be microscopic and actually non-existent much of the time (although actually there is always a twisting force on the suspended bearing and platter, due to the rotation of the platter mass), presumably the designer posited some degree of freedom of movement of the suspended elements in response to environmental forces.So, if you do mount the motor on the support structure, the movement of the suspension will cause relative motion between the (stationary) motor and the (suspended) platter (if we are talking about a belt drive). The belt would have to stretch and relax to accommodate this kind of movement, which causes a transient change in the length of the belt, which would cause an aberration of speed. That's all I was trying to say.
I can't name a bunch of suspended tables that are built this way or not built this way; I was surprised to read in your post that maybe lots of them are built with stationary motors, and I agree the reasons for doing that are obvious. I once owned an AR turntable, then a Thorens TD125, then a Sota Star Sapphire III. Those are the only 3 suspended tables I have ever owned, and I cannot recall how they handled this issue, respectively.
Edits: 04/27/17 04/27/17 04/27/17
> I once owned an AR turntable, then a Thorens TD125, then a Sota Star Sapphire III.
> Those are the only 3 suspended tables I have ever owned, and I cannot recall how they handled this issue, respectively.
Every one of the turntables you mention has their platter and tonearm mounted on a suspended sub-chassis, but their motor is mounted on a stationary plinth.
> I can't name a bunch of suspended tables that are built this way or not built this way;
That doesn't surprise me because all belt-drive turntables that I know of with a suspended sub-chassis have their motors mounted to a stationary plinth. I don't believe there are any belt-drive turntables built like you suggest---at least I've never heard of any.
Best regards,
John Elison
All good, but I was not suggesting or did not intend to suggest that suspended belt-drive turntables ought to have the motor mounted on the suspension, necessarily. Obviously, that would open another can of worms. I was pointing out that the typical design has this theoretical issue. I don't know how one would address this issue in the best way possible, maybe suspend the motor separately on a suspension that was linked to the main suspension so that the two move in synchrony but at the same time are isolated from one another as much as possible. It's an interesting engineering problem.
They both use similar (I think) separate sprung plinths for platter/tonearm, and for motor, with the suspensions tuned to work together, counteracting what Roksan believes is the effects or rotational torsion on the suspension caused by groove modulation.
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> It's an interesting engineering problem.
It sounds like an opportunity for you to redesign the belt-drive turntable.
Personally, it doesn't concern me in the least because the solution was developed years ago and it's called direct-drive. ;-)
Good luck,
John Elison
John: In my view your description would rather apply to true sub-chassis designs only, while "suspended turntables" would be a wider group also including for example the classic Dual belt-drive models with suspended "drive" ("floating chassis") and quite a few suspended direct-drives. Understood in a pretty wide sense, one could even call a Thorens TD280 a suspended turntable for sporting comparatively soft feet with integrated springs.
Greetings from Munich!
Manfred / lini
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