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Technics SL-1200MK2

Not trying to discredit anyone, you make a bearing mod which differs from the original design in the same way , care to explain why Dave ?

I'm not the professional Dave, that's your goodself old chap.


PS, the 3rd party has no knowledge of this, but did at the time, give his blessing to pass the information on if anyone is interested.
 
chris@panteg said:
Not trying to discredit anyone.
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Not trying at all, you are succeeding, if you can't see that no worries, others can.

What I object to was your hidden motives. And I have no desire to promote my products in this thread, or to discredit others. However if you will get the originator of your hearsay to come on this thread, then I will.

My issue was they you were hiding the fact that your "knowledge" was from a competitor of the product you were criticising. That isn't on in my book. :(
 
The third party was Vantage Audio. No actual need to hide the identity my mistake.

Not asking you to promote your products Dave, but I knew you wouldn't answer my question, and you knew it too, I know why you came on to this thread.
 
Shuggie said:
Are Vantage Audio trading again?
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I don't know , I understand they are dealing with the backlog of customers turntables but not taking on any new business .

I just thought the viewpoint of Vantage Audio on the SL1200mk2 is useful ,it does conflict with others ,and if it does look shady and deceitful on my part then
I apologise , lack of experience .
 
I found the post thought provoking, Chris. It's always enlightening to hear alternative viewpoints.
 
chris@panteg said:
Firstly the bearing, the original bearing has a single point of contact, at least two aftermarket bearings I know of use a separate ball bearing, adding an additional boundary surface compared to the original, this will increase noise and friction.
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Umm.. that isn't strictly true. I don't know the specific details of the two bearings you allude to but I do know the construction of many others that use a ball and shaft arrangement. What is usual is that the ball rests in a machined cone and the flat end of the shaft bears against the surface of the ball, sometimes the machined cone is in the end of the shaft and the ball bears against a thrust pad in the bottom of the bearing (much the same effect, just inverted. Because of friction differences between the cone and the thrust plate bearing surfaces the ball will remain static relative to one and movement will only occur at one surface - just having a secondary boundary doesn't increase noise.

I should also add that I am sceptical as to the quoted 'ideal weight' for the platter - what evidence is there to support the idea that 2.5kg is optimum other than second hand hearsay? The Technics uses a feedback loop to continually adjust speed -given that then the optimum platter weight (theoretically) is zero, having zero inertia and so able to instantly respond to corrective inputs from said servo.
 
Thanks for your thoughts Mark , interesting ,regarding the motor circuit , 2.5 kg is not mandatory but a general ball park figure , he did tell me that anything over 3 kg and the PPL is being pushed to its limit and noise will increase .

Here is a quote I have .

' The peak demand for the motor drive circuit is set in stone by virtue of the design and construction of the motor (coils, magnet position, etc, etc, etc) and nothing can change this. Altering the moment of inertia and the resulting change to rate of change of flux in the motor will take the motor and circuit out of limits and plain simply increase noise levels generated in the circuit.

And another which you may want to question ?

Something to add here is that installing a solid platter on the Technics SL-12XX series is not the answer at all as the OEM design incorporates a void underneath such that when the platter is rotating it generates a certain amount of air resistance. The designers used this resistance in their calculations as an air damping effect and factored this into the equation. Part of the reason the OEM platters are built they way they are (along with the practicalities of casting). Hence also the reason for keeping the plastic dust cover in place.
 
YNWOAN said:
I should also add that I am sceptical as to the quoted 'ideal weight' for the platter - what evidence is there to support the idea that 2.5kg is optimum other than second hand hearsay? The Technics uses a feedback loop to continually adjust speed -given that then the optimum platter weight (theoretically) is zero, having zero inertia and so able to instantly respond to corrective inputs from said servo.
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What would happen when you applied a torque to a zero mass disc?

Technics include the platter inertia and motor starting torque in their documentation for the decks. They are the values they are by design. Part of that design is obviously to enable a rapid start up and stabilisation and if you take away that requirement perhaps the best design would be different, but it seems unlikely to me that significantly changing the platter inertia alone is a good idea.

If you have access to a Technics with a working strobe you can see the effect of the PLL in the control loop, apply some braking with a finger, watch how the strobe markings move away slightly from their starting point, but how the speed remains constant. Remove the braking, the strobe markings return to their original offset. It's quite neat.

Paul
 
Paul R said:
.

If you have access to a Technics with a working strobe you can see the effect of the PLL in the control loop, apply some braking with a finger, watch how the strobe markings move away slightly from their starting point, but how the speed remains constant. Remove the braking, the strobe markings return to their original offset. It's quite neat.
Paul
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Yes it is, and quite different from most direct drives !
 
Hmm.. well the first part relates to the danger of making the platter too heavy but doesn't address why 2.5kg is supposed to be ideal. The statement seems to assume that mass is beneficial but only up to a point.

The second idea that the underside of the platter acts as an air break is highly dubious (exceedingly unlikely in fact). Some air resistance will occur whatever the platter construction but at the speed a platter rotates at it will be absolutely tiny and swamped by other issues. I addition,the void below the platter won't increase air resistance. If air resistance veins had been incorporated then I would say that such an 'air break' claim could potentially be made but as it is I would counter than the shape of the Technics platter is entirely the result of casting and post machining limitations, nothing more.
 
chris@panteg said:
The SP10 mk3 has a platter weighing about 10kg, the motor if I remember correctly had 32 or is it 48 poles ? Will have to check, its beast of a thing and quite rare.
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So the SP10's platter is similar in weight to the aftermarket platters being made for the SL-1200 who's stock platter/mat is 2.5kg. The SL-1200 motor has 12 poles and the SP10, 32 or 48.

I can't help but think that Technics knew what they were doing when they specified a different motor to be used with a heavier platter.

QaLdah.jpg


Here's a shot with the incandescent light in place about to play a most bizarre album.
 
tedmanzie said:
Both my mid '80s 1200mkII's came with the very heavy rubber mats, but the 12000mkII my friend bought new in the mid 90s came with a much thinner rubber mat - seemed like a cost cutting exercise.

Does anyone know where to get the original heavy mats? I lost both of mine and would like to replace them.
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From KABUSA website:


Technics Original MK5, M5G Platter Mat.
The thicker MK2 mat, 1/4" 17oz. has been officially discontinued. KAB still has stock on the MK5 mat which has the same scultured top, but is only 1/8" and 7 oz.

I imagine you can purchase a used mat from some audiophool "upgrading" their stock deck.
 
John said:
So the SP10's platter is similar in weight to the aftermarket platters being made for the SL-1200 who's stock platter/mat is 2.5kg. The SL-1200 motor has 12 poles and the SP10, 32 or 48.
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I don't think the number of poles is particularly relevant, but IIUC both SP10/2 and SP10/3 have 15 pole motors.

Paul
 
I don't see why the number of motor poles would be relevant to this issue either. However, as far as I know the 1200/1210 motor and that of the SP10 are not the same.
 
John said:
Here's a shot with the incandescent light in place about to play a most bizarre album.
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It's a remarkably sensible album and everyone should have a copy! (I have a UK United Artists 1st press).

PS I also have an orange that Damo Suzuki gave me.
 
I don't see why the number of motor poles would be relevant to this issue either. However, as far as I know the 1200/1210 motor and that of the SP10 are not the same.
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They're similar in principle. And one of the differences between the SP10/2 and SP10/3 is the 'upgrade' from a 2.9kg platter to a 10kg platter. So having a similar number of poles and very different platter mass tends to confirm that poles per se aren't relevant without having to dig into the maths.

Paul
 
Paul R said:
I don't think the number of poles is particularly relevant, but IIUC both SP10/2 and SP10/3 have 15 pole motors.

Paul
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Not sure about the specific number of poles in the various SP-10 models but this link specifies 20 in an earlier model with the lighter platter.

The SP-10 had a 20 pole 60 slot DC motor driven at 15 Volt. The platter reached nominal speed within half a rotation of the platter at 33-1/3 RPM. The player had two speeds: 33 1/3 and 45 rpm. These were adjustable. The pitch control had a margin of +/- 2%. Wow and flutter measured 0.03 %. Rumble values were -50 (DIN A) and -70 dB (DIN B). The weight of the platter was 6 lb. - appr. 2.720 kg. A wooden base plus acrylic cover were available as extras. Equipped with an oil damped Technics tonearm the turntable was named SL-1000. Without base and arm it was the SP-10.

http://www.soundfountain.com/amb/sp10page.html#MK2
 
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