Originally Posted by tlmusic
The LP actually sounded more pleasing than the analog tapes on the Ampex machine.
And this is a pretty good statement of why so many people like how LP sounds. It isn't because it's more accurate or has wider bandwidth --- how can it be more accurate than the master tape? Its various distortions are pleasing to the ear, and there's nothing wrong with that.
Originally Posted by tlmusic
CD's store an analog sound in sections. It stores one event of sound, then another event of sound and on and on. The data on the disk is read by a laser, which tries to read as best as it can and then then sound is converted back to analog so we can hear it.
You make it sound as if it's an intractable problem to read a CD accurately. When people have monitored the error rates of CD players reading normal CDs, they've found that the data is completely recovered, and accurate down to the bit.
For one thing CD's do not reproduce sounds above approximately 18000 CPS range. Some people say that humans can't hear that high, others claim it really affects the sound. LP's are not limited it that way. Apparently some LP's can store sounds up to 100,000 CPS!
CDs are pretty much flat and distortion-free to 20 kHz. I'm not sure where you got your 18 kHz number from.
LPs do have suprasonic response, but no one ever talks about how non-linear and noisy they are throughout their entire range. And then you have to ask the question of how important frequency response above 20 kHz (even if it's busted like LP's) is to the human hearing system.
A more common cause of 100 kHz response in LP isn't music-related. Scratches, dust, and other physical artifacts on LPs can create very high energy in the suprasonic range. This is why people who restore old LPs digitize them at very high sampling rates well above CD's, so that the noise artifacts can be accurately characterized, and then edited out. However, this really doesn't have anything to do with the musical information contained on LPs.
So on to the idea of "jitter."
Problems with speed consistency on a record will result in just what you might expect.
That's not jitter. Jitter is the instantaneous change in speed accuracy from moment to moment. When you play an LP too fast or too slow resulting in a pitch change, that's just the accuracy of the motor. Crystals or clock oscillators used for CD players characterize this as clock accuracy. The difference is that clock or motor accuracy is about a consistent error, whereas jitter is an error that changes moment to moment. It might be too fast for one clock cycle, and too slow for another clock cycle. Phase noise is another name for jitter than better describes the phenomena.
An analogy is a clock that consistently loses 1 second a day. That's your changed pitch. A clock that might gain 1 second, and then lose 1 second moments later has jitter.
Their effects are also completely different. Jitter (or wow in an LP system) causes frequency modulation of the music. Speed accuracy just causes a consistent pitch change.
Regarding CD jitter, to quote wikipedia, "In the context of digital audio extraction from Compact Discs, seek jitter causes extracted audio samples to be doubled-up or skipped entirely if the Compact Disc drive re-seeks. "
That's also not the jitter we're talking about. This passage only applies to when you rip a CD on a computer.