What sonic merits?
The short version.
The land/pit and pit/land transitions on a disc are ones, the rest are zeros. The shortest pit or land (3T) is 1001 and the longest (11T) is 10000000001. NRZI-NRZ-EFM removes the extra zeros so that 100100100100010 becomes 10011101. then the signal is passed to C1 and C2 where the error correction takes place. CIRC, error correction and interleaving takes place on the audio data using the subcode and parity data. The interleaving consists of switching the locations of the data so that in the case of consecutive errors they are spread among the good data. This means that what started as 100100100100010 on the disc, could be 10101001 or a very small part of the audio data of your favourite song. The audio data is sent to the FIFO buffer. It is the buffer that actually controls the rotational speed of the disc. Less data in the buffer, the disc speeds up and with more data it slows down.
The very short version:
A disc does not contain any "sonic merits" but coded data that is removed, decoded, decoded, corrected, decoded, corrected, decoded, stored and then after some delay sent to the DAC.
EDIT:
The first stages (except output is muted) there is no difference between a CD-AUDIO and a CD-ROM.
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High speed CD/DVD-R drives are used in duplication towers and automated duplicators where they are in service 24/7. Look at the TEAC/TASCAM equipment, most of their players are just CD/DVD computer drives. The truth is that the newer drives are far superior compared to the old, slow designs.
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you could have done this from the beginning:
The Unison Research Due Player are good example for what one might call fraud fraud supported ny the so called specialist press:
The Unison Due uses a 8829CD-KHM DVD-Loader from Stremunlimited. It is "audio only" thus it will be a KHM-313 from Sony.
Order it from Ebay, it won´t cost you more than a meal at a Burger Shop.
New KHM 313AAA Laser Lens KHM313AAA for Sony CD DVD KHM313A No Mechanism | eBay
This 13$ crap with tons of play in the gear, and plastic on plastic "rail"
This works in a 5000$ CD-Player.
Very likely that the servo board was made by Streamunlimited, because the Unison uses their loader. Pro-Ject uses the same boards and mechs, their Players "only" cost abot 500€
Talked to Streamunlimited @IFA, they did not have their CD/DVD solutions at display anymore because they focus on streaming.
This is why they were more open to talk about their Blue Tiger products. Bottom line:
Never did quality control on the mechs themselves They were dependend on what Sanyo and Sony gave to them and did not have influence in bettering the transport.
Again, this is why I started this thread!
Because none of the so called High Enders took the Effort to develop durable transports, besides (as far as we know) Esoteric and Burmester...
This is absolutely correct. The reason therefore is the fact, that all such small companies haven't the possibility to create those part, you ask for. And for this reason are by Linn ltd all transport components with cd and DVD transport (like Unidisc and CD12) out of production since several years (there are only HDD/network components for music reproduction available).
The first generation cd players from Philips, released between 1983 and approximately 1988 uses the best transport units ever made for cd:
CDM-0 until CDM IV. For pics of such transport go to the links under
http://www.diyaudio.com/forums/digital-source/75257-calibration-krell-md-1-cdm3.html
or the pics under
http://www.diyaudio.com/forums/digi...ega-solo-trio-cd-f1-first-edition-wanted.html
The only thing for replace is the laser diode itself (in very rare cases necessary, because the used ROHM RLD78 are more longlive than Sony SLD104, used in e. g. KSS-210A and KSS-272A)
http://www.diyaudio.com/forums/digi...d-philips-cdm-x-mech-they-want-resurrect.html
I think, the most easy solution to get the wanted results is that idea from me, for that I ask here the necessary steps:
http://www.diyaudio.com/forums/digi...-pcb-cdm0-cdm-0-cdm3-cdm-3-a.html#post4532122
BTW - I don't know transport devices for Blu-Ray and DVD in the same kind of Philips' CDM-0 or CDM-2 - i. e. high quality long live version.
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Hi kach22i,
The main thing we want to accomplish with any transport / mechanism is to isolate the sub-assembly that carries the head, CD and guide tracks plus disc motor. It is all designed to decouple that sub-assembly from any vibrations that may impinge on the CD player from outside or even internal sources. Adding another contact point on the top severely compromises efforts to isolate the CD and reading sub-assembly. Never mind internally generated vibrations from those bearings.
-Chris
That is true, but it is a question of scale. How much extra current is needed to track a defect. As Mark pointed out earlier, CD players routinely track defects far beyond the original standards allowed.
You most certainly can return new CDs with media defects. With low quality pressings, you will probably not find a good CD until the CD is re-issued. When you buy used CDs (I do as well), you are accepting that the discs could be defective, and the trade-off is price.
Well, that's a choice - isn't it? It is entirely up to you whether you buy good CDs or not. If it turns out that the content is great, why not buy a new copy of that one?
You can easily center the magnet if it is not perfectly centered. If there is too much play after the CD is chucked, you can also modify the profile of the clamping components to correct that issue as well. Call that "fine tuning" as is often done with firearms.
That's a fact of life, sorry.
If you look at any stable platter, you will see that it has bearings for the additional platter that constitute another contact point for vibration to enter the rotating system that we want to isolate from the world. Keep the basics in mind and you will see that choices become much more clear to see.
The main thing we want to accomplish with any transport / mechanism is to isolate the sub-assembly that carries the head, CD and guide tracks plus disc motor. It is all designed to decouple that sub-assembly from any vibrations that may impinge on the CD player from outside or even internal sources. Adding another contact point on the top severely compromises efforts to isolate the CD and reading sub-assembly. Never mind internally generated vibrations from those bearings.
Cost is always a factor. There are some problems that are too small to worry about compared to other issues. It's not an evil thing to consider performance vs cost, but a very real part of any project in any field.
-Chris
Hi kach22i,
Many thanks for your kind words.
-Chris
Many thanks for your kind words.
Then it is important that you both read and think. Asking questions is fine, but make sure they haven't been asked yet.
Within reason, but that suggests that we have an unlimited budget and there are no contradictory requirements. Sometimes it is impossible to make everything perfect from all points of view. Engineering is all about that fact of life.
Sure thing! Of course that means that your CDROM is now probably a two bay device and costs a great deal more than the rest of the computer. People would then simply buy a stand-along unit instead.
Sure, you install an add-on card. I have done that very thing.
No, but I cannot take the time to convince you of every single thing you think of is either the way to go, or not the way to go. These things you have to examine on your own. Once that has been done, explanations are much easier from this end.
That doesn't always work, and it isn't the topic of this thread either.
It won't happen. Sorry. Cheap transport sends sub-standard quality data to any DAC you might have. Garbage in = garbage out.
... and that is the focus of this thread. Anything else distracts from the goal.
True. However there is a time and place for these things. This isn't the place to question everything.
I'm glad you have learned. That is the purpose of every thread. But do feel free to comment if you notice something you can share that is directly related to what is being discussed. That is general advice that applies to every thread here.
-Chris
It is not only about cost and compromise. First you compile a list of specifications and targets. These could be anything. Cost or quality are obvious. Things like eye pattern or ground noise are not. You need to be able to fill in the numbers first or plan how you are going to find them. This is why I previously asked for clarification on what is a good eye pattern or acceptable ground noise produced by the servo systems. Numbers, numbers and more numbers. You cant design anything good without knowing the numbers.
Well.... again that wasn't what was being said in my post. It was about the sonic merits of a laser head NOT having to work hard to recover the data first and foremost. Also the sonic merits of less error correction having to take place.
I wasn't talking about sonic merits of speed accuracy either.
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If a CD contains no "sonic merits" I suggest you try finding music you do like.. (I'm not sure I understand what you were trying to say in that sentence).
Anyway, this sums up what I'm talking about:
And this is talking about the "poor quality parts" of a CDM1, a mech we consider today as being very well built! His measurements showed a great reduction in reading errors induced by vibration etc caused by the mech itself.
This is a thread about designing a mech. That of course depends on your own standards and goals, but if I were designing one I would be trying hard to reduce the impact of the mech itself on read errors or anything which may cause a audible difference down the road.
It would be great to be able to quantify the read-error reduction from the suspension set-up in the CD1 compared to the same mech without the suspension. I'll keep searching.. in vain I guess.
And this is talking about the "poor quality parts" of a CDM1, a mech we consider today as being very well built! His measurements showed a great reduction in reading errors induced by vibration etc caused by the mech itself.
This is a thread about designing a mech. That of course depends on your own standards and goals, but if I were designing one I would be trying hard to reduce the impact of the mech itself on read errors or anything which may cause a audible difference down the road.
It would be great to be able to quantify the read-error reduction from the suspension set-up in the CD1 compared to the same mech without the suspension. I'll keep searching.. in vain I guess.
And some anecdotal evidence from Stanley Beresford (a Philips trained engineer) that CRIC has a sonic effect when being enacted: NVA 'TFS': 'The Future Statement' lands at Marco Towers... - Page 19
Why exactly are the newer drives far superior?
Something about the speed of the servos used to align the laser reader?
It is it the rotational speed serving to aid accuracy in reading?
Hi kach22i,
The entire question of a bit perfect rip is one that will always have two sides in disagreement. I agree with the quote you posted in that respect.
The two discs the engineer was talking about are ones I still have. Philips 5 and 5A. Really horrible sounding discs and I am sick to death of them. The 5 is the "perfect" disc, the 5A has defects printed on the surface. The 5A cost me $250 CDN, the 5 was $50 CDN. I bought those after the training I received at the Philips facility here in Canada. I had a 1 on 1 training session right at the beginning of the CD players introduction.
I will disagree on one point. The Philips transports were not the greatest examples of how to do things. They had built in problems like the flex cable breaking and the lens support sagging over time. They injected an oscillator generated sine wave into the arm servo in order to find the edges of the track. This modulated the RF pattern to some degree making the eye pattern a bit fuzzy. If you had reason to align the swing arm, forget it. That task is factory only. I did it once. Even the technical staff at Studer-Revox gave up on aligning these in the field (any location outside the factory). They have some defects that they are very sensitive to, just like any other CD mechanism. To attempt to create swing arm mechanisms without the original jigs and know how would be an exercise in futility. They are much more difficult to align than any other mechanism I have seen - ever. One of the goals of this project is to create a serviceable transport.
-Chris
The entire question of a bit perfect rip is one that will always have two sides in disagreement. I agree with the quote you posted in that respect.
The two discs the engineer was talking about are ones I still have. Philips 5 and 5A. Really horrible sounding discs and I am sick to death of them. The 5 is the "perfect" disc, the 5A has defects printed on the surface. The 5A cost me $250 CDN, the 5 was $50 CDN. I bought those after the training I received at the Philips facility here in Canada. I had a 1 on 1 training session right at the beginning of the CD players introduction.
I will disagree on one point. The Philips transports were not the greatest examples of how to do things. They had built in problems like the flex cable breaking and the lens support sagging over time. They injected an oscillator generated sine wave into the arm servo in order to find the edges of the track. This modulated the RF pattern to some degree making the eye pattern a bit fuzzy. If you had reason to align the swing arm, forget it. That task is factory only. I did it once. Even the technical staff at Studer-Revox gave up on aligning these in the field (any location outside the factory). They have some defects that they are very sensitive to, just like any other CD mechanism. To attempt to create swing arm mechanisms without the original jigs and know how would be an exercise in futility. They are much more difficult to align than any other mechanism I have seen - ever. One of the goals of this project is to create a serviceable transport.
-Chris
What the test disc 5A (printed on underside, dots on topside) does is push the error correction close to or beyond its limits, where it can not fully reconstruct the data and this is where concealment takes place. The same happens when playing any dirty or scratched disc. If you monitored C2, or even better, E22 and E32 you would see when this occurs, know that the disc is bad and clean or replace it.
My advise is to stop reading the anecdotal rubbish or at least first try to understand the real technology behind it. A good place to start would be: "The Compact Disc: A Handbook of Theory and Use"
My advise is to stop reading the anecdotal rubbish or at least first try to understand the real technology behind it. A good place to start would be: "The Compact Disc: A Handbook of Theory and Use"
Hi Mark,
It's the music on them. A tone would have been far more preferable. You figure I have spent years and years listening to music selections I didn't care for. From the mid 80's to now with no end in sight. Why they didn't use a tone, I'll never know. The tone makes it very easy to detect when things get too much for error correction and concealment.
-Chris
It's the music on them. A tone would have been far more preferable. You figure I have spent years and years listening to music selections I didn't care for. From the mid 80's to now with no end in sight. Why they didn't use a tone, I'll never know. The tone makes it very easy to detect when things get too much for error correction and concealment.
I have. It's just as easy (easier) to monitor the RF envelope to check the condition of these test discs. Any servo issues will show up here, as well as surface defects and the reaction of the tracking servo to them. One thing is for certain, I'm not buying any more of these discs. I would buy another Pierre Verany test disc.
-Chris
Yes, but you can't see when the concealment is active. I believe that a lot of the confusion about error correction is caused by not knowing what is error correction and what is concealment during playback. A disc could have good tracking and still contain many C2 errors.
I wasn't testing players, only discs. Cut a thin groove from ID to OD using a Stanley knife. Test with zero, one, two, three grooves. Watch the BLER, E22, E32 increase until it is audible or stops playing.
I wasn't testing players, only discs. Cut a thin groove from ID to OD using a Stanley knife. Test with zero, one, two, three grooves. Watch the BLER, E22, E32 increase until it is audible or stops playing.
So, any verdict yet? It seems as you folks talk about the transport as mechanics+controller... For my part the transport is the mechanical moving parts+motors and maybe the laser unit. The electronics controling it is the next step.
Just make it strurdy, replaceable parts, doing from CD to HD-audio including SACD - did I forgot something?
Regards
Just make it strurdy, replaceable parts, doing from CD to HD-audio including SACD - did I forgot something?
Regards
That's fair comment
Although the Stan Curtis stuff is only anecdotal because his measurements are his own and not published (because he's not a funded research body) and it was decades ago when it had commercial application. That is the measurements regarding registered read errors of all types from mechanical problems of the mech which when addressed were significantly reduced.
Hi Mark,
Since I can't affect what the chip set is designed to do, all I can concentrate on is sending it the best data I can. That issue is under our control. It all boils down to starting with the cleanest, most stable RF pattern you can set up. After that, what happens to the audio is determined by what choice has been made with regards to which ICs are used.
-Chris
Very true. Some chip sets don't tell you what they do for concealment. That would be good information to have.
Since I can't affect what the chip set is designed to do, all I can concentrate on is sending it the best data I can. That issue is under our control. It all boils down to starting with the cleanest, most stable RF pattern you can set up. After that, what happens to the audio is determined by what choice has been made with regards to which ICs are used.
Great advice for everyone.
-Chris
I'll just keep reading this thread for a while longer, it's entertainment.