I recently bought a 2-disc CD album. Popped them into my Sony multidisc carousel and find that one disc plays fine but the other is really dreadful. On first couple of attempts it just sort of "jitters". I tried it in different positions in the player and no difference. No scratches or visible damage at all. The seller claims that he tests all the CDs he sells on a PC before he posts them. I tried the dodgy disc on my desktop PC and sure enough, it plays without issue. I have about 350 CDs that play well on the Sony player but this is the first disc that doesn't work.
Why might this be? Manufacturing defect? Player laser out of alignment? Something else?
Why might this be? Manufacturing defect? Player laser out of alignment? Something else?
Hard to say. If it is just one disc then probably an issue with that disc.
1/ Does the disc look as silvery as it should or has it a yellow tinge to it?
2/ If you put the disc on top of another (not from the same set) do the centre holes line up exactly?
3/ If you hold the disc to bright light can you see through it more than you should. Any holes or a mottled effect?
1/ Does the disc look as silvery as it should or has it a yellow tinge to it?
2/ If you put the disc on top of another (not from the same set) do the centre holes line up exactly?
3/ If you hold the disc to bright light can you see through it more than you should. Any holes or a mottled effect?
Cal - That is truly weird.
Mooly - I tried your three suggestions. Nothing glaringly obvious but I did notice a very slight difference when holding them both in front of a strong light. The disc that doesn't play right is slightly less transparent than the other one. Not patchy but evenly all over.
Mooly - I tried your three suggestions. Nothing glaringly obvious but I did notice a very slight difference when holding them both in front of a strong light. The disc that doesn't play right is slightly less transparent than the other one. Not patchy but evenly all over.
That sounds a bit bizarre Cal, can't just compute that one tbh.
The whole handling of the data is different playing from a stick vs playing a CD. Are you ripping the disc as an MP3 or .wav or .wma or similar? Have you tried the stick in another car? Weird.
Hmmm. Next step with that would be to look at the recovered RF on a scope and see how it compared to a known good disc. You would look at amplitude and overall 'Q' or quality of the diamond shape in the eye pattern and also whether there was noticeable jitter.
Could the less transparent disc have a 'film' of something over it. Contamination sort of film. Ordinary household multipurpose spray polish (not beeswax or ones with oil in them) might be worth a try. Just a little on the disc on both sides and give it a real polishing with a clean duster. It won't harm it, I do that to all discs as soon as I get them.
The whole handling of the data is different playing from a stick vs playing a CD. Are you ripping the disc as an MP3 or .wav or .wma or similar? Have you tried the stick in another car? Weird.
Hmmm. Next step with that would be to look at the recovered RF on a scope and see how it compared to a known good disc. You would look at amplitude and overall 'Q' or quality of the diamond shape in the eye pattern and also whether there was noticeable jitter.
Could the less transparent disc have a 'film' of something over it. Contamination sort of film. Ordinary household multipurpose spray polish (not beeswax or ones with oil in them) might be worth a try. Just a little on the disc on both sides and give it a real polishing with a clean duster. It won't harm it, I do that to all discs as soon as I get them.
Update: I have cleaned the disc with a clear liquid domestic product having no abrasive content. Still not playing in my main CD player. It does work in my Desktop CD tray. I hooked up a second Sony player, exactly the same player model as the other one and the CD does play, although it sounds a little tinny, and there was one momentary dropout somewhere in the middle of the side.
I am a bit out of my depth here but I put forward a theory. We all know that the sound quality of a vinyl record can vary widely due to lack of care in one or more of the production stages and there can be issues that will cause it to skip or sound really bad, IGD, etc. When played on different turntables with different cartridges with more forgiving characteristics it might play back much better. Is it possible that some minor deficiency in the manufacturing process laying down the laser "track" might be causing the CD problem? Maybe one player or CD tray in a computer can do a better job of tracking a slightly wonky recording. A possibility? I don't have the equipment to check alignment or focus of the laser lens but I'm doubtful that would help since about 300 discs play well on this unit.
I am a bit out of my depth here but I put forward a theory. We all know that the sound quality of a vinyl record can vary widely due to lack of care in one or more of the production stages and there can be issues that will cause it to skip or sound really bad, IGD, etc. When played on different turntables with different cartridges with more forgiving characteristics it might play back much better. Is it possible that some minor deficiency in the manufacturing process laying down the laser "track" might be causing the CD problem? Maybe one player or CD tray in a computer can do a better job of tracking a slightly wonky recording. A possibility? I don't have the equipment to check alignment or focus of the laser lens but I'm doubtful that would help since about 300 discs play well on this unit.
Computer drives which are DVD/CD units tend to cope better with marginal discs than do older audio only players. It is also quite possible that both disc and player could be a fault and that the two together just push things to far. Suppose the player is 80% OK and your 300 discs are 90 to 100% perfect. It plays them all. Suppose the disc in question is only 70% OK. That may well play OK in many players but not in one that is a bit below where it should be.
Without proper testing and using a scope I'm afraid it all becomes guesswork. A check of the RF would show in an instant if that disc alone was marginal for output quality.
The best you can say at this stage is that if the player is OK with 300 discs and not this one then chances are the disc has a problem.
Without proper testing and using a scope I'm afraid it all becomes guesswork. A check of the RF would show in an instant if that disc alone was marginal for output quality.
The best you can say at this stage is that if the player is OK with 300 discs and not this one then chances are the disc has a problem.
The Compact Disc was designed to cope with minor scratches on the surface - they are out of focus.
Scratches from the label side can do much more harm as they destroy the pits.
But generally the system is redundant. The clicking comes more likely from the data loss
because the laser does not hit the same groove after the scratch.
It is generally two horizontal servos for the laser, for coarse (sled) and fine movement (lens).
But sled, lens and tracks/scratch are almost never aligned tangentially when
the data for tracking is lost by a scratch.
Swing arms from Philips were better at tracking safely over scratches as there is only one horizontal servo.
Chances were higher to hit the same groove again.
Also how well a disc is centered might play a role.
To my understanding computer drives are designed to read in sectors and reposition more precisely on a track.
I might talk rubbish about the sector thing. But in fact I could rescue some CDs by ripping them.
Two days ago I stumbled over a CD that had a clear pressing defect:
A mirror like spot (dark on the photo but in fact reflective), where the pits were missing.
Very likely a defective stamp.
A pity, as the 2019 recording is relatively rare, "Seven Limbs" by Douglas J. Cuomo - see photo
Back to topic:
My guess about your double CD is that one CD is more out of center than the other.
Should be audible by mechanical noise when you compare both CDs in a Computer drive.
Or the stamps were worn out so the pits became "blurry".
They changed it on one disc but forgot to do it on the other...
Scratches from the label side can do much more harm as they destroy the pits.
But generally the system is redundant. The clicking comes more likely from the data loss
because the laser does not hit the same groove after the scratch.
It is generally two horizontal servos for the laser, for coarse (sled) and fine movement (lens).
But sled, lens and tracks/scratch are almost never aligned tangentially when
the data for tracking is lost by a scratch.
Swing arms from Philips were better at tracking safely over scratches as there is only one horizontal servo.
Chances were higher to hit the same groove again.
Also how well a disc is centered might play a role.
To my understanding computer drives are designed to read in sectors and reposition more precisely on a track.
I might talk rubbish about the sector thing. But in fact I could rescue some CDs by ripping them.
Two days ago I stumbled over a CD that had a clear pressing defect:
A mirror like spot (dark on the photo but in fact reflective), where the pits were missing.
Very likely a defective stamp.
A pity, as the 2019 recording is relatively rare, "Seven Limbs" by Douglas J. Cuomo - see photo
Back to topic:
My guess about your double CD is that one CD is more out of center than the other.
Should be audible by mechanical noise when you compare both CDs in a Computer drive.
Or the stamps were worn out so the pits became "blurry".
They changed it on one disc but forgot to do it on the other...
Attachments
I have a similar problem with my sony blu ray play ( that I use as a transport ), it plays nearly all CDs, but some ( annoyingly RUSH, led zep ) don't on the first try but on the second try they sound VERY jittery and mushy - but you can faintly hear the mudic. I thought it could be a copywrite issue, sony trying to stop copying. Perhaps it's reading a high bit rate track that the SPDIF link ( between the sony and DAC ) can't cope with.
Interestingly, the disc I'm having trouble with is Disc 1 of Physical Graffiti.
Seeing it plays fine on your computer, try to re-burn that cd and see what happens to the burnt copy in the Sony
Cheers George