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Old 3rd February 2010, 06:45 AM   #141
Mooly is offline Mooly  United Kingdom
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I have a few older CD's (all classical) that use pre emphasis. Mostly EMI label and all Japanese pressing. Think Denon used it too...must check.

Also have a Philips and a Denon test disc that has tracks to check for correct de emphasis operation too... once I would have had the enthusiasm to copy these tracks with various programs and see if the data is preserved... but now lol

Re eye patterns and burning... I find (on my burner) that the best eye pattern (when disc played back on normal player) comes from the higher burn speeds... it's much cleaner and noise free particularly in the lower part of eath "cycle". Perhaps that's an anomaly of my burner.

Also... a new (fab quality CDM12.4 of Japanese manufacture) I fitted to my own player a few years back didn't always like some CDR's... it wouldn't always recognise them. On this CDM12 the RF is of unbelievable quality but the amplitude was "high" at around 1.7volts pk/pk... so I reduced it in steps and found that 1.6 volts gave 100% recognition... and that it could be lowered to below 0.9volts before any readability issues crept in.
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Old 4th March 2010, 03:33 AM   #142
anatech is offline anatech  Canada
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Hi malcontent,
Well, you have just proved beyond any doubt that your software is lying to you. Each point of light represents total loss of some data. The C1 error correction may be able to restore the missing stuff with no loss in quality at all. However, with a "perfect" CD, there is an error rate associated with it, C1 errors, but errors none the less. With less than ideal discs, you can fully expect a much higher C1 flag rate, coupled with the appearance of some C2 flags. Those are defined as "unrecoverable errors", and they are. About all you can so is hide them in some way.

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Fast rippers, which use the drives firmware to rip at high speeds for encoding to your mp3 player are a completely different topic then secure rippers.
No, they are the same process. The allowable error rate is the only thing different between the two. Now, if you begin talking about a data type ripper as opposed to a music CD ripper, you have got that point exactly. Also, defining the result as intended for an MP3 file, you've given the ripper a very wide latitude. MP3 files have been subjected to "lossy compression", so errors from a CD source are insignificant compared to what you get with an MP3 file.

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Again, my point is to eliminate the problems of primitive optical encoding, by ripping the data to a proper error corrected format.
Primitive optical encoding? That's immaterial since the goal of transferring the information to any media is for an error free operation. Anything you write or transmit down any media must be formatted in agreement with the standards for that media. The data must be in a legal format, which has nothing to do with whether the data starts out with or without errors. It can't go anywhere until the data and encapsulation is valid (not correct). I think some people may be getting that confused a little.

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How else does one get accurate data from cds without redundant rereads? (Who cares how long it takes? It is done once and done unattended.)
This has been my point all along. In fact, I have witnessed rips that could not complete when they are commanded an error free rip. The entire question on error free rips is disproved when the first multiple read attempt occurs, because most CD players can only read a track once without "skipping". They are on a linear read, one time through without interruptions when playing normally on a CD player.

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Either way, my experience with actually ripping data is that mis-read data is an occasional aberration (read: inaudible).
Well, no. This is not true at all. Serious errors tend to come in bunches, which will also ensure you develop uncorrectable errors (C2) as well. Any C2 error may be audible or not depending on your state of mind and the machine's quality. If we are to believe that effects of super clocks are audible, then C2 errors are audible for sure. Then there all the other "upgrades" that are sure to improve the sound quality.

I will tell you one thing that has been proved empirically over many years. Properly aligning the servos and head alignment brings an audible improvement.

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Your vast knowledge of disc players and their possible flaws notwithstanding, the fact is the errors are rare (with the exception of damaged discs, which probably sound better ripped anyway.) and cd players based on obsolete technology are easily bypassed.
Hey, all anyone can do is to state what they know. The rest is entirely up to you. Every technology has error mechanisms and flaws to some degree. Even your computer network has built in methods for correcting data. It calls for the data to be sent again (now that's high tech! ). This represents a problem with voice transmission since the latency is so important. You even have a very limited time for buffering. Resending data can not happen. CD data correction is beginning to look less obsolete if you ask me.

Why do you assume that the data transfer is a one time deal? Write-able CDs have a lifetime, and the sun accelerates this to a high degree. Tape is no better here, and so are hard drives. Nope, CDs are a perfectly valid technology.

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I am sure a cd player would refuse to play the disc at all.
Don't bet on this. Some will, and some will not.

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So even my worst ("unplayable") cd has fewer than a dozen C2 corrected errors in 45min. of music. Although they are clustered in tiny sections.
See, what did I say before on this? I must say that a dozen C2 errors is further proof of what I have been saying.

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They are still not audible. (to me.)
Fair enough, but they are there. C2 errors are serious enough to really give your DSP chip a workout! It is doing a good job.

Understand that the original premise of this thread was an error free, bit perfect data transfer. One single C2 error is all it takes to create an image that is not anywhere near "bit perfect". Performance degrades further depending on the condition of the transport and it's alignment. Things never get better over time either.

-Chris
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Old 4th March 2010, 03:51 AM   #143
anatech is offline anatech  Canada
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Hi Mooley,
Quote:
Think Denon used it too...must check.
I think you're right about that. Emphasis reduces high frequency distortion because you can now work with more bits to represent the signal, then lower the gain at these frequencies on playback.

Quote:
once I would have had the enthusiasm to copy these tracks with various programs and see if the data is preserved... but now lol
I hear you there!

Quote:
I find (on my burner) that the best eye pattern (when disc played back on normal player) comes from the higher burn speeds... it's much cleaner and noise free particularly in the lower part of eath "cycle".
Expected. They have to optimize the EQ and electronics for some speed, may as well go for an area where most users will operate them.

Quote:
Also... a new (fab quality CDM12.4 of Japanese manufacture) I fitted to my own player a few years back didn't always like some CDR's... it wouldn't always recognise them.
Different reflectivity, so the slice level (Yamaha terminology I think) is different for those discs. Many early machines had problems with recordable CDs, this was solved as they moved to servos to automatically correct for this and other parameters.

Quote:
On this CDM12 the RF is of unbelievable quality but the amplitude was "high" at around 1.7volts pk/pk... so I reduced it in steps and found that 1.6 volts gave 100% recognition... and that it could be lowered to below 0.9volts before any readability issues crept in.
I found that the quality was too variable with these and the VAM-1202 No adjustments or corrections can be made, and the RF servo PCB may be supplied with the head. No schematic, no parts list and no support, well not much until they are out of warranty.

With stories like these, I completely understand why Creek uses CDROM drives for computers and why Cyrus designed their own CD transport completely. I am impressed that you went through it to figure out wher the best performance was, then correct your machine to those levels.

Best, Chris
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Old 4th March 2010, 07:07 AM   #144
Mooly is offline Mooly  United Kingdom
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Hi Chris,
I think the days of finding any decent CDM12.4's are long gone unfortunately... as you well know, the quality (certainly of the ones I have come across lately) has been grim.
A pity because it can be a superb performer "when it's right". Even the platters on many don't run true, causing "outer edge wobble".
The little plastic "damper" on the CDM12.4 platter motor spindle always makes me laugh... CDM12.1's have to make do without. Think the 12.4 was originally a CDROM pickup ? or designed with that in mind.

Whenever I come to replace the Micromega (I have one new CDM12.4 pickup left "in stock"... of Singapore manufacture), a major consideration will be the pickup used and whether it's easily available as an original spares item at a good price.

I remember first coming across "Data Slicers" in the early days of CD during a three day Sony course... we really pulled the theory apart that week.

Touch wood, up to now I haven't come across a CDR of mine that has deteriorated (if it plays perfectly I "assume" there isn't a problem... haven't 'scoped the early ones), but I do store them cool and dark.

take care
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Old 25th April 2011, 01:21 PM   #145
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Quote:
Originally Posted by planet10 View Post
I am not saying that the amount of magnetism will affect anything, just pointing out that the blanket statement that a CD has nothing magnetic in it is a false statement. SY's analysis indicates that it is probably not large enuff to have any affect (but not a proof).
I am trying to stimulate discussion of possible mechanisms, and why they will or will not affect things. I do not have a position on these devices
but i would like to see a clear & intelligent discussion of why or why-not.
For instance, we can dismiss the bits-is-bits, because we are dealing with an analog representation that could be misinterpreted, Here is an image of idea, practical ideal, and something more typical in a cheap CD player (maybe they are even worse in really cheap players -- anyone have some real world eye-pattern captures they can post?) dave
Interesting facts - thank you therefore and for the URLs in the following posts #75 ana #76.
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Old 25th April 2011, 07:39 PM   #146
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I rip with EAC which checks hashes of rips of a CD so if several people have ripped a cd and got the same resultant data its certian your rip is good. Ocasionaly a tiny speck of dirt causes an error in a rip wherupon I clean the disk by rubbing it on my shirt. Errors with reading a CD are simply not an issue, after all my computer does it reliably at many times 1x cd speed.
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