What does Jitter sound like?

Shadorne - the positions of the pits in the CD are a form of timing information that can cause jitter as they are read. How this affects the PLL/buffering in the CD player depends on the design of the CD player. It is evidently important though. Rewriting a disk on CD-R with low jitter is an audible improvement on virtually all CD players I have tried. I mod a LOT of transports and players, so I get to try many different ones. This is good evidence that the pit locations are actually important.

Steve N.
Empirical Audio

Steve,

I woudl refer you to Nika Aldrich "Digtal Audio for teh Audio Engineer"

Quote:Page 353 "A digital recorder will store exactly the same information regardless of how jittery the clock"

Therefore according to Nika it makes no difference how many recordings or re-recordings or CD-R's you make.....ONLY a conversion to Analog or to Digital (where a clock is necessary) does jitter enter (from the clock).

A lot of people still seem to not buy-in to jitter effecting sound. I get the impression people think that since their PC software loads fine from a CD without error, then their audio CDs should too. But it's different. Perhaps someone can explain what's happening in 10 words or less. Jitter occurs at different places-at the place where a cd is read and then between any (every) 2 points in the circuitry. Anyone want to take a stab at how this effects sound? E.G. "The edges of the bits are not square because of X, causing some 1s or 0s to get missed" or "The edges of the bits get fuzzy, causing the dac to approximate some bits.". Then there is latency jitter. I'm not saying either of these is correct, just giving illustrative examples. I'm no expert; looking for the experts to chime in.

Shadorne - you are missing the point. It is not the data in the copy that is different, as explained in the paper you cite. It is the jitter DURING real-time playback that is different. This is the distinction.

Steve N.

Bigamp - Sooner or later the folks that dont understand the jitter thing will hear it or they will eventually upgrade their systems to the point where they hear it. Until then, it is like trying to explain how the earth looks from space.

Jitter is simply inaccuracies in the timing of the bits that make up the data stream. It is like a clock that ticks every second. If the clock ticks at exactly each second time interval, then it is said to have no jitter. If some ticks come at .999 seconds and others at 1.001 seconds, then the overall time will be accurate over many seconds, but there is jitter in the timing. This is how actual real-time systems work. They all have some amount of jitter.

The effect of this jitter on the D/A conversion is to create frequency modulation in the analog output. This means that the point at which the top of the cymbol crash was supposed to occur actually occurs maybe 1 nanosecond later and then the trailing ringing of the cymbol comes maybe 1 nsec earlier. The rate of this change can be anywhere from 10hZ to 100kHz or higher. If there is only one sample that occurs at the wrong time, it will never be heard, but typical jitter signature is usually a constantly changing time error. This is why it is audible. The brain detects these things just like it detects moving objects with eyesight.

The time error has both amplitude and frequency or spectra characterisitics. Each CD player or computer audio device has different amplitude and spectra for its jitter, so they can sound very different from each other, even though the data is always the same. Data errors are very uncommon for both CD players and computer audio. Jitter is the difference that you are hearing, if you hear a difference.

Steve N.
Empirical Audio