I see many of the same type medium priced audio CD/cassette players that come in for routine cleaning from area schools. Many times the complaint is "CD not working". Before doing any cleaning I test them with a variety of my own CD's and often times I cannot confirm any problems with many of these machines. I have asked that the teachers include with the particular offending player any particular CD which has failed to play for them but usually I never get any. My own test CD's are just standard CD's and vary in that they are different sizes. Some consist of two tracks, others are four, one is ten, etc. Is there any relationship between how many tracks are recorded on the CD and whether or not it may or may not play on a given questionable machine ? Most of these machines have been in service for about five or six years. I don't like giving them back NPF but a bad laser on one of these is a death sentence so I would like to be able to know if there is a way without getting too involved to accurately assess this. Thanks, Lenny.
Clearly, the students are trying to play dirty or scratched disks. Contrary to the belief that digital optical media are largely immune to surface defects, even minor scuffs can render a disk unplayable. (I recently had to replace a disk with a nearly invisible defect for ths reason.)
Tell the schools they MUST provide a non-playing disk, or the player will be returned and the school charged the full repair cost.
My thought is that it could be a problem with the CDs, or some types of CDs. I would not have a hard time believing that CDs coming from an education environment have at times been handled roughly, been allowed to get dirty, are not always stored correctly and are not in the best shape ever as a result. This may be the entire problem.
I don't know what kind of shape your test CDs are in. If you don't already have some, I would recommend adding some that are not in the best of shape--garbage discs that have been scratched up in places and things like that.
Discs such as CD-R and CD-RW types may not play well on these players due to reflectivity differences from pressed discs. Errors in the burning process can also cause problems at playback time.
Some of the discs may also be troublesome due to cheap methods of reproduction that result in hard to read discs or errors on the disc.
If anything, I'd think the first few tracks would be the hardest, as the spin speed is highest there.
It is not hard to find a CD player that is ten or more years old and still working fine. I've even seen some old (7+ years) CD players removed from businesses where they played eight hours a day or more, and in the few cases of ones that had failed, all faults found were mechanical in nature--slipping belts, worn out gears, bad spindle motors, that sort of thing. Most of these units were from well known manufacturers such as Pioneer and Sony.
Therefore I'd find it unlikely that the units you are servicing have bad lasers, especially if they work on your test bench.
Exactly - well made CD players tend to be very reliable as far as lasers go (more reliable than lasers in DVD players or CD-ROM drives), I've got a first generation Philips CD101 that still plays fine after 25 years (even on CD-R's but obviously won't read RW's).
Actually there's a thought - don't suppose the schools are trying to save cash and using CD-RW's to allow re-use of discs and the players don't officially support them but allow the occasional disc to play anyway (some old players may have borderline ability to read CD-RW's even though not designed to) so when one doesn't they assume it's a fault?
Sometimes yes, sometimes no. Here's my take on it.
I don't think that the issue is the number of tracks. Rather, it's the total duration of the contents, and how the CD was made.
CDs play from the inside out. Those CDs which are almost "full" (up to 72 minutes) have data which goes quite far out towards the edge of the CD. There are a couple of reasons why the outer edge may be more difficult for a CD player to play:
- Dust and grease and tobacco-smoke tar can build up on the "rails" on which the laser mechanism slides back and forth. The inner portions of the rails may be less gunked up, because the sled "wipes" these portions of the rails during almost all playbacks. The outer portions are wiped less often... and so if you try to play a CD which uses the whole disc diameter, the sled can run into a sticky portion of the outer rail, and fail to track evenly... hence, skipping.
- CDs can wobble, if they aren't sitting flat-and-even on the center spindle. This can happen if the spindle is damaged, has debris on it, or if the CD's center hole is damaged or isn't evenly punched. The effect of a vertical wobble will be more pronounced out at the outer edge, and the laser will have more difficulty tracking the disc and maintaining a proper focus on the groove.
The discs themselves can be a big part of the problem:
- CD-R and CD-RW discs are inherently harder to track than a "manufactured" (molded and aluminized) CD. The dye layer (CD-R) or phase-change layer (CD-RW) has a lower contrast than the molded pits on a manufactured CD. This leads to a lower signal level as seen by the playback electronics, making it harder for the servo to maintain position and focus on the track, and raising the bit-error rate. If a CD player's laser is getting old and its output level is dropping, the lower reflectivity can become a significant problem.
- Many (most) CD-R discs these days are of the "extended time" variety - they hold up to 80 minutes of content, as opposed to the 72 minutes of a standard CD or CD-R. These long-play discs push right up against the edge of the Red Book standard in several ways - the spiral tracks are packed together quite closely, and the "pits" and "lands" burned into the dye layer are at the lower size limit of the standard. This tight packing once again makes it harder for the player to maintain tracking and focus lock.
- "High speed" CD-R discs use a dye laser which is quite laser- sensitive, so it can be "burned" with a short exposure... it may have even a lower contrast than a standard CD-R's dye layer. Vibration of the disc and drive during a fast burn can further reduce the quality of the pits and lands, making tracking even more difficult.
- Discs which are used in an institutional setting (classrooms, public libraries) are often in poor physical condition... fingerprints and scratches. Tracking problems abound, as do low-level data errors which can cause popping and muting. My wife frequently borrows books-on-CD from our city library. They're all CD-R, mostly extended-length, probably burned at very high speeds, and they're usually dirty and scratched.
She can't use a portable CD player with these... we've tried several and they all suffer from skipping problems. Our home CD deck will usually play them, but even it suffers from skipping occasionally (which never happens on CDs from our own home collection).
On a few occasions I've "ripped" a troublesome disc, and then burned a replacement CD-R. The replacements play fine on all of the CD players we've tried. The ripping of these damaged discs often takes a very long time... the drive and software end up retrying certain sections of the disc dozens of times in order to reconstruct the data correctly.
I've found that a good, careful cleaning of the lower CD surface with plastic cleaner often helps (I use the Novus brand). Usually a clean-and-polish is enough to allow for a quick rip-and-burn. In a few cases, I've had to use the Novus 2 scratch-remover to buff out big scratches.
So... to sum it up, I suspect that the problem you're seeing may be an interaction of several things: an aging laser whose output is dropping, hard-to-read discs (low-reflectivity extended-play CD-R, probably in poor physical condition), and maybe some crud buildup on the lens or rails.
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Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
I find there are two kinds of blanks available, ones that look yellow (gold or silver) and those that look blue. Audio players, especially ones made in the last century can not read blue disks. I think the capability to read them came in around 2002 or so.
The space between sectors is well defined in the various standards. There is a problem when you burn a CD where the data is not available when the drive wants to write it. In the old days (1991) the drive wrote zeros in that spot, producing a useless disk. Later the drives started detecting the errors and producing buffer under-run errors, usually causing the burning process to abort.
Several systems exist to prevent the errors, such as "burn free", or "seamless link", and so on. They work by detecting the buffer under-run and stopping the burn in such a way the disk is still readable. They still produce what according to the original standard is an unreadable disk, but by the extended standards they are perfectly ok.
As far as I know, CD ROM drives from around 2000, and all DVD ROM drives, except for the very early single speed ones can read these disks without an error, but audio players can not. Possibly the new ones with read-ahead (anti skip) can, but most of the players out there can not.
My experience with CD-ROMs and old drives has been that if you expect to read a disk, you have to turn off buffer underrun protection, use yellow blanks, and record it at no faster speed than it will be read at.
DVD burners have better laser positioning, and the burn speed is less critical.
In any case, if you are not careful, you can easily burn an audio CD which will play on a computer, and not on an audio player. Been there, done that.
There was a thread a long time ago on the audio groups about using Armour-All, a car polish on the disks. In every case it improved the reading (sound) of audio CD's, but many turned cloudy after a few months. No one knew what the long term effect was of them turning cloudy, but that was so long ago (early 1990's) that there should be some somewhere if one can locate them.
Dave, on a personal note, a high school friend that went to school with you just contacted me facebook and I literally just sent him an email detailing what was going on in my life and mentioned that you and I occasionally follow-up each other's postings.
Geoff.
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Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM
Phthalocyanine - almost transparent to visual light frequencies. This results in discs whose bottoms look silver or gold, since the color of the reflective metal layer shows through without being modified very much. This was the type of dye used on the first CD-R discs developed by Taiyo Yuden.
Cyanine - light blue to the eye. This results in discs which look light to medium blue (against a silver-colored reflector) or green (against a gold reflector).
Azo - somewhat darker blue than cyanine. This seems to be the most recently developed dye type, and I'm not sure how common it is.
I haven't noticed any consistent difference in audio-player compatibility between *good* phthalocyanine, and *good* cyanine discs. In theory, Orange Book (CD-R) discs were *supposed* to be playable on any Red Book audio CD player.
CD-RW is a different story - the phase-change layer has such a low contrast that older CD players often can't get any sort of signal lock on them at all.
The Red Book standard allows for some amount of variation and tolerance.
72-minute CD-R discs (if well made) have a track spacing and rotation rate which sits right in the middle of the Red Book tolerance range.
The 80-minute discs squeeze the spacings down right to the lower limit of what a Red Book player is supposed to accept.
The actual "sector" structure isn't manufactured into a CD-R blank. Instead, the track is molded into the disc, with a slight side-to-side "wobble" with a well-defined period between peaks. When the CD-R drive spins the disc, its laser servo follows the track, and in doing so it develops a sinusoidal voltage in the horizontal tracking circuit which corresponds to the track wobbling. The drive then uses a phase-locked loop to monitor the frequency of the wobble, and adjust the drive's rotation speed to the correct rate. It then "burns" the actual pits and lands into the dye layer, defining the block structure of the disc as it goes... and it's the burned pits and lands which the CD player (or CD-ROM drive) uses to address and find the data.
Yeah, an audio disc with a "burn free" hiccough does end up with a nonconforming data pattern in its output bitstream. A standard audio CD player can lose lock on the signal and mute.
That's a good way to go about it.
For the *best* compatibility with audio CD players (new or old) it can help to buy the type of blanks which are intended to be burned in "real time" CD-R recorders (i.e. at a 1x rate). These tend to use a nice, thick dye layer - they're optimized for long laser exposure. They're actually a lot more like the original first-generation CD-R discs, in some ways, than they are like modern high-speed discs.
I'm rather sceptical of the claims of improved sound, except to the extent that the treatment might have slightly reduced the rate of error correction.
Armor-All Protectant really should never have been used on CDs. It isn't formulated as a plastic cleaner or polish - it's a silicone emulsion - and I don't find it surprising that it reacted badly with polycarbonate plastic.
The only cleaners or scratch removers I'd suggest that people use on a CD, are those which are specifically designed for safe use on polycarbonates. The Novus products I mentioned (Novus 1 [cleaner] and Novus 2 [light scratch remover and polish]) are of this sort. I wouldn't use Novus 3 (heavy scratch remover) as it is specifically
*not* recommended for polycarbonates - only for acrylics.
I kinda suspect that they're ruined, unless somebody has managed to figure out a way to buff off the surface crazing.
Neat! Could you email me his address, or email mine to him?
--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
On a couple of scratched DVD-RW, I did manage to sand the gouges out of the surface with 600, 800, 1200 then use the novus to follow up. There is usually plenty of depth to the surface. there are buffing machines out there though. A local Vid rental shop will turn them for $20. If you just can't bear to lose the data.
One issue not mentioned, the newer drives must properly identify the media type and manufacture for proper burn or play of newer media. A firmware update on the drive may be available.
The last issue I have dealt with is Op failure. If the media doesn't play on cue, the show must go on without further ado so guilt is assigned to a unit and the execution is swift lest the actual guilty party be discovered and discredited. This is also known as the failure code 1d10t.
I guess if your customers are truly bothersome, and require regular punishment and discipline or berating. I would much prefer the "full routine maint" of running a cleaning disk and leave a disclaimer that media defects may affect performance (The political fix). If the cost on a particular unit gets out of hand there may be a scandal worse than just retiring a worn unit for replacement.
It'd probably help for the OP to collect a set of known-to-be- troublesome discs, as well as those with specific known defects and/or test patterns.
I've still got, somewhere, a set of the Pierre Verany test CDs. One disc in this set has a calibrated set of tracking defects... you can see just how much of a glitch a specific CD player is able to track over, and what its error correction and concealment behavior is. If I recall correctly, the Verany disc also has some tracks which will let you look at the quality of the "eye" pattern from the photodetector, and do some tracking-system adjustments.
This one is out of print, I believe, but there's a somewhat similar disc by Burosch available from MCM:
formatting link
The OP could probably make some slightly-harder-to-track CDs, by using cheap bargain-brand high-speed high-density CD-R discs and burning them at the highest speed possible. Burn a few with tracks that go all the way out to 79 minutes and close-to-the-end seconds. Then, take two or three and scuff them on a table-top, add fingerprints to your liking, and try 'em out.
This won't be a properly-calibrated "bad disc" suite, but it'll give some sense as to just how robust a particular player is.
Give the player a decent cleaning (lens and rails), check the eye pattern and tracking, and if necessary tweak the laser and tracking adjustments per the manufacturer's spec. Then, see if it'll play good discs out to the edge, if it'll play scratched-up cheap CD-R discs to the edge, and if it'll track through the Verany (or similar) test defects without losing its mind.
In the absense of a known-to-reproduce-the-problem test disc from the user, that's probably about as good as you can do.
--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
What software did you use to rip the damaged disks? I ask because my young son has managed to scratch up a bunch of his mother's favourite CDs & DVDs, so I'd like to recover them.
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W
. | ,. w , "Some people are alive only because
\\|/ \\|/ it is illegal to kill them." Perna condita delenda est
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I agree with Dave's 'sum it up' Which is pretty much the case in lots of situations.
I recorded my first data CDR on a gold HP disc in a 1x HP SCSI burner on a computer running NT4. That was back when discs cost 15 bucks each and you literally held your breath, crossed your fingers while the disc was burned and finalized.
Taiyo Yuden was responsible for the dye that gave regular CD players the ability to read CDR.
Since I use Linux, I used the de-facto standard: "cdparanoia". This is available both as a standalone ripper, and as a library which is incorporated into GUI packages such as GRip.
If I were to do it on Windows, I'd probably use Exact Audio Copy, which I understand does much the same thing.
--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
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