Turk 182

cd transport or dac ?

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Super Dealer

Why on earth would you use belt drive for a mechanism that needs to control rapid changes in rotational speed.

Keith

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22 minutes ago, PuritéAudio said:

Why on earth would you use belt drive for a mechanism that needs to control rapid changes in rotational speed.

Keith

hi keith

is the cd not spinning at a constant speed then ?

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Super Dealer

No, belt drives by their very nature expand and contract, I wouldn’t choose a belt to rotate a platter even at a steady rotational speed.

Keith

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Posted (edited)
1 hour ago, PuritéAudio said:

Why on earth would you use belt drive for a mechanism that needs to control rapid changes in rotational speed.

Keith

Because the innovative braces-driven CD transport designed by renowned UK engineers Cannon and Ball failed to gain much industry traction.

I understand they did latterly propose a joint development mechanism to CEC, which would have offered the complete security of both belt and braces, but sadly with little real tradition of keeping your keks up in Japanese culture, the offer was declined and audiophiles everywhere were simply left to wonder 'what if...'

Edited by notevenclose
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3 hours ago, Turk 182 said:

hi keith

is the cd not spinning at a constant speed then ?

Quote ...

“Audio CD players read their discs at a precise, constant rate (4.3218 Mbit/s of raw physical data for 1.4112 Mbit/s (176.4 kB/s) of usable audio data) and thus must vary the disc's rotational speed from 8 Hz (480 rpm) when reading at the innermost edge, to 3.5 Hz (210 rpm) at the outer edge.”
 
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49 minutes ago, chebby said:

Quote ...

“Audio CD players read their discs at a precise, constant rate (4.3218 Mbit/s of raw physical data for 1.4112 Mbit/s (176.4 kB/s) of usable audio data) and thus must vary the disc's rotational speed from 8 Hz (480 rpm) when reading at the innermost edge, to 3.5 Hz (210 rpm) at the outer edge.”
 

hi chebby

thanks for that - i understand now !

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4 hours ago, PuritéAudio said:

No, belt drives by their very nature expand and contract, I wouldn’t choose a belt to rotate a platter even at a steady rotational speed.

Keith

thats interesting - maybe the material the belts that cec use are a special material ?

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Super Wammer
18 minutes ago, Turk 182 said:

thats interesting - maybe the material the belts that cec use are a special material ?

They probably wouldn’t need to be anything other than good quality for the speed and mass involved.  Any system like this would probably use a sensor on the CD ‘platter’ to feed back the actual speed to the motor.  This would then tweak the motor to provide the correct resulting speed.  A sort of continuous feedback loop. 

But I agree it’s a bonkers way to drive a CD, even if it can be done.  A classic audiophiles’ solution to problem created by imaginative marketing, rather than one that actually exists!

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12 minutes ago, Nopiano said:

They probably wouldn’t need to be anything other than good quality for the speed and mass involved.  Any system like this would probably use a sensor on the CD ‘platter’ to feed back the actual speed to the motor.  This would then tweak the motor to provide the correct resulting speed.  A sort of continuous feedback loop. 

But I agree it’s a bonkers way to drive a CD, even if it can be done.  A classic audiophiles’ solution to problem created by imaginative marketing, rather than one that actually exists!

They have a great reputation especially the more expensive ones. I guess that the fast speed of spinning of a CD means that there aren't measurable speed variations.

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From my limited understanding of a ships mechanical systems. Any thing that spins   generates a wobble. So when we have a motor spinning a pump, despite the bearings in the motor, the pump still has its own bearings to remove that wobble at the exact place where the drive shaft enters the pumps body. Same applies for CD mechsims too. A non belt driven CD player is basically a motor spinning a CD directly without any means to check it's mechanical wobble apart from its own internal bearings. That is where belt drives come in my limited option. A motor with its inbuilt bearings to damp it's own wobble, driving a CD mechanism which again has its own bearings, so the Spinning CD is damped better. I could be completely wrong, but Iam just extra polating from how ships huge mechanical systems with lots of loads and mechanical stress and vibration are designed 

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Super Wammer
39 minutes ago, newlash09 said:

From my limited understanding of a ships mechanical systems. Any thing that spins   generates a wobble. So when we have a motor spinning a pump, despite the bearings in the motor, the pump still has its own bearings to remove that wobble at the exact place where the drive shaft enters the pumps body. Same applies for CD mechsims too. A non belt driven CD player is basically a motor spinning a CD directly without any means to check it's mechanical wobble apart from its own internal bearings. That is where belt drives come in my limited option. A motor with its inbuilt bearings to damp it's own wobble, driving a CD mechanism which again has its own bearings, so the Spinning CD is damped better. I could be completely wrong, but Iam just extra polating from how ships huge mechanical systems with lots of loads and mechanical stress and vibration are designed 

I risk straying beyond my technical know how but I think balancing motors is a well proven technology these days, so in practice the vibrations are negligible. 

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Super Wammer

You would also need to consider how the motor is mounted if direct drive, or how the spinning  platter is supported for belt drive etc.  The CD itself can oscillate even with belt drive, hence The TEAC vrds system that clamped the disc or the Pioneer stable platter system to try to eliminate the vibration of the spinning CD changing the distance between the CD and laser lens.

My Roksan Attessa CDT is direct drive but with a magnetic clamping puck which both clamps and adds mass to change vibration harmonics.  The drive mechanism is suspended on 4 springs to further isolate the drive and I added mass to the motor support plate to lower its resonance further.

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Posted (edited)
11 hours ago, Nopiano said:

They probably wouldn’t need to be anything other than good quality for the speed and mass involved.  Any system like this would probably use a sensor on the CD ‘platter’ to feed back the actual speed to the motor.  This would then tweak the motor to provide the correct resulting speed.  A sort of continuous feedback loop. 

Nope. What you're describing is an early generation Japanese direct drive turntable. Which is not how the CEC works, although CEC actually has a long history in OEM turntable manufacture.

The belt drive is part of the equation, but the heavy stabiliser weight, motor isolation and the suspension are key parts of the equation as well. Basically, it's a lot closer to a Linn than a Technics.

Quote

But I agree it’s a bonkers way to drive a CD, even if it can be done.  A classic audiophiles’ solution to problem created by imaginative marketing, rather than one that actually exists!

Says a man who has never heard one. ;-)

Remarkably consistent descriptions across the entire range – http://www.cec-international.com/CEC-The Drive/PAGES/s22.html

Latest review by Roy Gregory http://www.cec-international.com/CEC-The Drive/PAGES/s03.html

Edited by notevenclose

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Super Wammer
2 hours ago, notevenclose said:

Nope. What you're describing is an early generation Japanese direct drive turntable. Which is not how the CEC works, although CEC actually has a long history in OEM turntable manufacture.

The belt drive is part of the equation, but the heavy stabiliser weight, motor isolation and the suspension are key parts of the equation as well. Basically, it's a lot closer to a Linn than a Technics.

Says a man who has never heard one. ;-)

Remarkably consistent descriptions across the entire range – http://www.cec-international.com/CEC-The Drive/PAGES/s22.html

Latest review by Roy Gregory http://www.cec-international.com/CEC-The Drive/PAGES/s03.html

Thanks for the links - certainly a huge number of glowing reviews.  A bit like DCS then, except for the belts?  (Do you think the bits look any different when replayed on a belt drive?)

You are quite right, I’ve never heard one.  I wonder if a rip on a £25 drive stored on a nice hard disk sounds any different when replayed via a CEC DAC? 

I am glad to see diversity, however, and that means it’s a bit like is the top Technics turntable better than a Tech Das, doesn’t it?  

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1 minute ago, Nopiano said:

Thanks for the links - certainly a huge number of glowing reviews.  A bit like DCS then, except for the belts?

I've only heard DCS equipment once, around a decade ago. On that basis, my gut response would be 'Jesus, I hope not...' but that was a long time ago and in a system which for my tastes no front-end could have redeemed (and which at high volume emptied a large room as effectively as machine gun fire), so probably unfair to judge solely on that. 

But as far as I know, until very recently DCS had abandoned physical media, so no, probably not very much in common at all.

1 minute ago, Nopiano said:

I wonder if a rip on a £25 drive stored on a nice hard disk sounds any different when replayed via a CEC DAC? 

Compared to what? A CD on a CEC transport? To me the file invariably sounds inferior regardless of the DAC used. In my system at the moment that's more clearly demonstrated by the DAC in my amp than my CEC DAC.

1 minute ago, Nopiano said:

I am glad to see diversity, however, and that means it’s a bit like is the top Technics turntable better than a Tech Das, doesn’t it?  

As I said, the belt-drive thing is just one factor. Doesn't mean it's the 'one true path' any more than it is for turntables. Generally speaking though I do have a clear preference for top-loading CD mechanisms with high quality mechanical engineering and invariably some type of puck/clamp/brick in the process. Apart from CEC, I really rate top-loaders from Pro-Ject, Reimyo and Zanden. 

Inconveniently for any tentatively coalescing dogma, there are exceptions, one of my all-time favourite CDPs remains the Resolution Audio Opus21, which uses a cheap DVD drive, and one of these days I'd like to hear the Origine player.

Personally I'd probably rather have the Technics, primarily because looking at the latest TechDas it seems highly improbable I'd be able to heave the bugger up the stairs.

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