I have tested thousands of discs using CD-Cats sa3 and other expensive CD test equipment (100,000 US$). I also used NERO DiscSpeed and Opti Drive Control (<30 US$) with different CD/DVD(-R) Drives. The results between different players are always very close and disc related. I would even say that a Plextor CD-R drive will read at lower error correction than the CD-Cats. This is maybe partly because it is able to adapt its read strategy. It is like comparing an old LADA with a new MINI.Not saying that you should not prefer the old LADA.
Doesn't that say that CD-Rom drives all read the same rather than CD audio mechs, from the heavyweight's of the past through to the modern, pressed steel cheap ones of today?
Interesting about Plextor - I've kept Plextor CD-writers for burning CDs over others..
I've opened up many many CD players and watched them play. The clamp's themselves are sources of vibration! Their magnets are rarely centred properly and cause eccentric movement of the disc which can be seen. Subtle but visible.
Also I rarely see the edge of a CD in sharp focus when spinning - it is often blurred meaning it's vibrating. Therefore lots more re-focusing going on and all the resulting extra servo action, EMI potential and ground noise.
Those are real observations which some some sort of clamping of the whole disc would solve.
Of course, arguable whether it improves the sonics aside from anecdotal evidence from some designers that read errors are improved and their own sense of improvement...
Have you thought about the electronics side of things? Laser power boards etc for longevity?
Somewhere I have an 80s magazine with a DIY laser power board for the CDM1 - a much stiffer supply.
Hi NATDBERG,
A warp in the CD (defective media - replace) is very unlikely going to be sorted by the stable platter. You can't see it anymore though and that must feel better. The clamping forces required to flatten a warped CD are far beyond the force most clamping mechanisms can apply.
A warped or bent disc table is another actual fault that should be repaired. Again, this is not the normal operating mode for that CD player.
In any event, you are talking about specific special cases.
EMI potential and ground noise is a function of how the electronics were designed. There shouldn't be any EMI generated at all, and ground noise is designed out (or should be)
-Chris
Are you talking about vibration or wobble at once per revolution? If it is vibration, something is broken in the disc motor. The machine is therefore in a fault state and needs to be repaired. A wobble is something the servos are designed to tolerate. A stable platter will not fix an off-center disc.
A warp in the CD (defective media - replace) is very unlikely going to be sorted by the stable platter. You can't see it anymore though and that must feel better. The clamping forces required to flatten a warped CD are far beyond the force most clamping mechanisms can apply.
A warped or bent disc table is another actual fault that should be repaired. Again, this is not the normal operating mode for that CD player.
In any event, you are talking about specific special cases.
I think you mean to say that the disc is warped, not vibrating. Within reasonable limits, the focus servo will track properly. However, that disc is defective. If normal CD players cannot track it, a stable platter one will not either. The fix is to replace the defective CD. CD players are not supposed to play everything that can be inserted if they are out of mechanical specification. Again, you are talking about special cases, and a stable platter can not apply enough force to flatten a warped CD.
EMI potential and ground noise is a function of how the electronics were designed. There shouldn't be any EMI generated at all, and ground noise is designed out (or should be)
Counting the C1 flag per revolution or frame would give you the actual error count. This directly leads to an averaged metric that can be used to compare mechanisms.
This would only be an issue in cheaper CD players. A non-issue really, because noise on the laser supply directly modulates the laser beam, and that shows up in the RF / eye pattern. It isn't a problem.
-Chris
A few of the relevant Red Book specifications:
Eccentricity +-0.2 mm.
Disc unbalance < 11 gmm.
Max. deflection +- 0.4 mm.
Max. deflection over one revolution +- 0.3 mm.
This means that a player must at least be able to play such a disc and in practise a lot worse.
The edge of the disc is transparent and it is the printing and/or the edge of the aluminium layer that gives the impression of deflection and eccentricity.
Eccentricity +-0.2 mm.
Disc unbalance < 11 gmm.
Max. deflection +- 0.4 mm.
Max. deflection over one revolution +- 0.3 mm.
This means that a player must at least be able to play such a disc and in practise a lot worse.
The edge of the disc is transparent and it is the printing and/or the edge of the aluminium layer that gives the impression of deflection and eccentricity.
A wobble at each revolution caused by most magnetic, sprung clamps.
Even if all those CD are warped and all those CD mechs faulty, then in designing a new one you surely want to ensure it has an extrememly robust motor, shaft and bearing (over-engineered) AND you want it to do something about warped CDs - afterall you can't control each CD press plant! And all CDs I've seen playing in real life have blurred edges and so have vibration.. that vibration must be within redbook tollerences and therefore a better designed mech will do something to combat that... surely?
Hi NATDBERG,
Could be the base of the forcing cone.
Could be the shape of the magnetic clamper.
Could be the shape or size of the CD.
Take your pick, but the magnetic clamp doesn't normally cause these problems, and they don't vibrate!
-Chris
Why? Defective is defective. If the mech can track it, great.
Sure you can. Return defective CDs, vote with your dollars. Ask Mark what happens when his quality slides. I'm going to bet he doesn't allow that to happen.
No it isn't! Mechanical pressure clamps suffer the same problems.
Could be the base of the forcing cone.
Could be the shape of the magnetic clamper.
Could be the shape or size of the CD.
Take your pick, but the magnetic clamp doesn't normally cause these problems, and they don't vibrate!
-Chris
Small divesrion: I used to salvage the Drive motors out of CDROM drives . When their crappy plastic mag rings were replaced with discrete Neo mags , their stators rewound .. these made for Surprisingly Good Hobby motors.
For little cost. Some of these motors were multi arm/pole things of a few inches diameter Instant Torque and of Stepper motor rotational accuracy
Why do CDplayers, even bespoke ones?
Still use 25 Cent brushed motors.
Couldn't be costs as CDROM/dvd write drives are ~30$.. at best
For little cost. Some of these motors were multi arm/pole things of a few inches diameter Instant Torque and of Stepper motor rotational accuracy
Why do CDplayers, even bespoke ones?
Still use 25 Cent brushed motors.
Couldn't be costs as CDROM/dvd write drives are ~30$.. at best
Maybe because of multiple speed? Just a guess. But as I wrote before,
first generation CD-Rom drives looked "better". I.e a brass platter in an
Apple "Superdrive" (DVR-103 made by Pioneer as far as I remember)
Let´s assume, the Sharp LT022MC was widely used, APC must be more or less the same?
Anyway, modifying an existing APC or building a new one:
Here i a comparison of the Sharp diode and one from Rohm one one sheet-
(The Rohm uses 2 diodes 660nm and 780, I cut the 660 data for clarity.
But the important data of astigmatism of the Sharp LT022 is missing.
And again, an APC for the Sharp LT022MC in a Sony CDP-502...
Attachments
Eeerrr, 52x CD Red-book reading would be unusual
but ...
52x computer,
is normal and would be ... normal
Couldn't you easily compare them with EAC,
ie a read @ low with real-time CD alorithims
vs
52x speed and
CD-ROM type reading, with multiple passes and amalgamation, CD ROM style,
and way more error correction [CD ROM type] compared to plain Redbook CD ...
better, no?
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Hi AudioLapDance,
I haven't a clue when it comes to data CDROMs beyond knowing the error correction is totally different, and more effective. My world stipulates that an CD read is a one shot deal, you either get it or not. The only multiple attempts occur when the player loses lock with the CD itself. The data is already lost when that happens.
-Chris
I haven't a clue when it comes to data CDROMs beyond knowing the error correction is totally different, and more effective. My world stipulates that an CD read is a one shot deal, you either get it or not. The only multiple attempts occur when the player loses lock with the CD itself. The data is already lost when that happens.
Creek did that already. They used computer CDROM drives.
-Chris
A DIY 2012 thread on a similar topic, last page with a post from someone which has auditioned many drives - liked the CD1050-A best.
http://www.diyaudio.com/forums/digital-source/206427-diy-cdplayer-audio-analogue-like.html
2010 review:
UNISON RESEARCH UNICO CD PRIMO
Unison Research Unico CD Primo | Hi-Fi | Review | AVHub
............
Unison Research Unico CD Player Reviewed
By: HomeTheaterReview.com, January 4, 2009
Unison Research Unico CD Player Reviewed
Unison Research's other CD player, the bigger brother to the Primo is the "Due"
Sources - Unison Research - Official Website
http://www.streamunlimited.com/products/optical-storage/8829-cd_specification.pdf
http://www.avhub.com.au/news/hi-fi/unison-research-cd-due-408974
If you are wondering why I'm posting this, it's just an informal inventory of what certain manufacturers were (or are) using.
http://www.diyaudio.com/forums/digital-source/206427-diy-cdplayer-audio-analogue-like.html
2010 review:
UNISON RESEARCH UNICO CD PRIMO
Unison Research Unico CD Primo | Hi-Fi | Review | AVHub
............
Unison Research Unico CD Player Reviewed
By: HomeTheaterReview.com, January 4, 2009
Unison Research Unico CD Player Reviewed
Unison Research's other CD player, the bigger brother to the Primo is the "Due"
Sources - Unison Research - Official Website
http://www.streamunlimited.com/products/optical-storage/8829-cd_specification.pdf
http://www.avhub.com.au/news/hi-fi/unison-research-cd-due-408974
If you are wondering why I'm posting this, it's just an informal inventory of what certain manufacturers were (or are) using.
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Hi kach22i,
A computer CDROM has everything going against it. It's very slender and power efficient. That means that the tray fits in there too, as does any vibration control. It runs off a noisy computer power supply and can not be allowed to generate too much heat either. All this for a cost to compete in the computer parts market. The audio section is really an afterthought as most play through the sound chip set on the motherboard. So, forget them spending much on that feature. The main functions will be transferring data on and off DVD discs, so that is where the money goes. So even if you could trick someone into spending $100 on this product, you still do not have enough money to improve audio performance much.
The economics of the situation do not support using a CD or DVD drive for audio CD playback. Besides, I can't think of any problem using a plastic lens for the laser. Even many cameras (with much higher performance requirements) use a plastic lens. None of this supports the supposed superiority of a CDROM drive over purpose built transports. However, for you this might be just the ticket. Go buy one and be done with it.
-Chris
Probably just buffer memory. Teac / Tascam's history for high end audio does not include CDROM drives. They will generally build something massive for that.
Really? In a CDROM drive yet.
You have got to be kidding! CDROM drives for computers are commodity products that retail between $12 and $35 CDN. Those are mostly plastic and will not use any hand lapped parts at all. If a human hand has to touch anything for finishing, you can expect that product to sell >$100 easily. I just don't see this from a company like Teac / Tascam. Those guys are not afraid to breach >$5,000 for top flight efforts.
A computer CDROM has everything going against it. It's very slender and power efficient. That means that the tray fits in there too, as does any vibration control. It runs off a noisy computer power supply and can not be allowed to generate too much heat either. All this for a cost to compete in the computer parts market. The audio section is really an afterthought as most play through the sound chip set on the motherboard. So, forget them spending much on that feature. The main functions will be transferring data on and off DVD discs, so that is where the money goes. So even if you could trick someone into spending $100 on this product, you still do not have enough money to improve audio performance much.
The economics of the situation do not support using a CD or DVD drive for audio CD playback. Besides, I can't think of any problem using a plastic lens for the laser. Even many cameras (with much higher performance requirements) use a plastic lens. None of this supports the supposed superiority of a CDROM drive over purpose built transports. However, for you this might be just the ticket. Go buy one and be done with it.
-Chris
A mech might be able to track it but it will require more error correction and the over-working of focus and tracking servos. And it is actually from your own posts in the past from which I have understood that a hard-working servo has the possibility of effecting sound via EMI interference often transmitted via the laser head ribbon cable and also effect the ground plain.. At least I thought it was you - some experienced CD player engineer here on DIYAudio.
You think I can return my secondhand CDs? I'll try... You think I'd get very far then returning ALL my hundreds of CDs, even deleted ones and I'd get a brand new collection back from somewhere? I've not bought a brand new CD in a long time..
I want a CD mech which will get the best sound out of my current CDs and not have to search for perfect ones... If that means flattening out tiny warps via a clamp or vacuum system then so be it but the result will be a better sound wihtout having to worry whether the CD is good or bad..
I clarified that they pretty much introduce an unballanced spin which causes a wobble, not vibrate. The magnets used are rarely centred within the plastic circle they are mounted in and when the clamp engages rarely do the magnets sit perfectly around the centre of the CD - they just attract in general to the centre of the spindle without much alignment. I'm thinking here of some great CD players like Sony 555es or Marantz CD94 - anything with a sprung, magnetic clamp I've used. As you say, they still manage to read so I guess the designers consider it a cost compromise success...
The clamping methods used in something like the CD701 VRDS is different because it is the mech being brought up to something solid, the VRDS platter, and the two mate together very well. Same goes for heavy pucks which sit perfectly in the centre.
If one is designing a good mech from the ground up, why would you allow compromises? Might as well just use something off the shelf if so.. Being "good enough", to be able read this and that isn't the point . Surely it's about designing and building one which sounds better due to attention to design and taking those extra steps?
I'm here to learn, and you certainly seem to know a lot.
However, cannot any system be designed to circumvent it's shortcomings?
What I mean is, can't the power supplies be split/dedicated and upgraded from those of a computer when designing a CD player?
The audio section a complete redo from that of a computer?
I do not mean to offend with my questions, please keep that in mind. I am not an adversary.
Some people have had the idea to find something cheap and maximize it as part of their exercise/design (that boombox derived project for example).
Some people have the idea of finding a drive used in some high priced CD player which is also used in a much cheaper unit, and using that as their transport (like me).
Others like the originator of this thread, have the idea of starting from scratch, or as near as possible, and making a better mouse trap/CD player.
In each case there is a learning curve, and perhaps something to be shared.
I don't want to hi-jack the thread anymore than I already have, so I'll just grab some popcorn and watch the show from now on. Learned a lot already.