What am I hearing???


~~~~Hello,
I hope someone can explain why on some cd's the long piano notes sound slightly warbled. Not the normal vibration from the piano's wires. Am I hearing laser trying to track info on a non-concentric disc? I noticed a lot of cd's data area slightly non-concentric to edge of disc. Shouldn't the laser be able to trace imperfections? Warranty time? Starting to bug me, RATS!

Just The Facts
By
fbi
Calanctus: Well, given that those posters all gave *different* explanations for time smear, which of them sounded convincing to you?

Given that this is a problem with only some disks, the source of the problem is almost certainly the disks themselves. I'd hate to see this guy sent on a wild goose chase to find a cable that will fix a problem that can't be fixed.
I agree with Bomarc. Regardless, you don't need a reason to buy a new CD player other than you want to buy a new CD player.
My guess is that piano may be slightly out of tune. What you describe is the beat frequency of 2 or more strings that are not quite in tune. If oyu hit or pluck 1 string then hit or pluck another that is out of tune, they will sound as 2 distinct notes. As you tighten the 2d string to match the 1st, you will hear a distinct wavering, rapid at first, then as they approach in-tunedness, the wavering slows, then disappears. You say you hear it on more than 1 CD - maybe pianos are harder to keep in tune than we think.

It seems hard to believe cables could store and release enough energy to produce something so clearly audible, especially since the storage times are so short (they occur at the speed of electricity, which is much faster than sound), and since the amount of energy storage is so short. In order to get a beat frequency, the cable would have to be altering the frequency of the signal it is storing and releasing. My understanding - tho limited- is that cables store and relesase a tiny fraction of the signal, resulting in out of phasse remnants dumping back into the signal, but still the same frequencies, with differences in amplitude relationships. The effects I've heard from cable changes are more of a focussing of low level detail, and changes in dynamics, especially at frequency extremes. It is unusual for any component other than a source (i.e. a wobly turntable, stretching tape, etc, as mentioned) to be able to change the actual content of the music.

I've also heard clipping sounds coming from tweeters. This happens when there is a lot of upper midrange content, like soprtanos, fairly high piano notes, especially fairly pure tones, held for a while. I think it is the tweeter screaming its head off at the lower end of its range before crossing over to the midrange. While it may not sound like the music's that loud, it is the same proinciple as driving a bookshelf speaker with very large amounts of bass - you get similar distortions.
Calanctus,
I'm one of those who offered an explanation of dielectric effect in cables causing time smearing, but I was only responding to Stehno's mention of that effect. I did not mean to imply this could cause piano note warbling. Sorry if I was unclear about that.

I quite agree with Bomarc that cable time smearing, while often audible, could never cause note warbling. The usual audible effects of time smearing in cables are harshness, haziness and the smearing of multiple voices into a homogenous mass of sound. Pitch change is never a result IME.

I also agree with Bomarc that laser problems, transport speed irregularities and non-concentric CD's are not to blame. Neither is jitter. A CD player is not a turntable, digital is not analog. I've already suggested tape stretch or speed irregularities in the original (analog) recording and mastering equipment, as well as a way to test that hypothesis.