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...ställa in programmen för automtrippning, bara sätta in skivan sen så swishar det till i nån minut sen så är det rippat, indexerat, skivomslag nedhämtat mm.

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The offset is the measure of your CD-Rom's inaccuracy in reading the proper location on the disc. For example if EAC wants the drive to read sector 10000, the drive would actually reads 10500. Fortunately EAC has all the tools you need to find and correct the offset. While 500 sectors seems like a lot it is only a tiny fraction of a second. Below is a formula for measurement on an audio CD. The offset in no way affects the sound quality - you can produce fine discs without setting it, but they won't be true, exact clones of the original.

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Jitter is the deviation in or displacement of some aspect of the pulses in a high-frequency digital signal. As the name suggests, jitter can be thought of as shaky pulses. The deviation can be in terms of amplitude, phase timing, or the width of the signal pulse. Another definition is that it is "the period frequency displacement of the signal from its ideal location." Among the causes of jitter are electromagnetic interference (EMI) and crosstalk with other signals. Jitter can .... introduce clicks or other undesired effects in audio signals... The amount of allowable jitter depends greatly on the application.

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Jitter and Digital Copies
The key is in the playback, not in the transfer
Many well-known devices have high jitter on their outputs, especially DAT machines. However, for most digital to digital transfers, jitter is most likely irrelevant to the final result. I said "most likely" because a good scientist always leaves a little room for doubt in the face of empirical (listening) evidence, and I have discovered certain audible exceptions (see below). Until we are able to measure jitter with widely-available high-resolution measuring equipment, and until we can correlate jitter measurements adequately against sonic results, I will leave some room for doubt.

Playback from a DAT recorder usually sounds better than the recording, because there is less jitter. Remember, a DAT machine on playback puts out numbers from an internal RAM buffer memory, locked to its internal crystal clock. A DAT machine that is recording (from its digital input) is locked to the source via its (relatively jittery) Phase Locked Loop. As the figure above illustrates, the numbers still get recorded correctly on tape, although their timebase was jittery while going in. Nevertheless, on playback, that time base error becomes irrelevant, for the numbers are reclocked by the DAT machine! I have not seen evidence that jitter is cumulative on multiple digital dubs. In fact, a Compact Disc made from a DAT master usually sounds better than the DAT...because a CD usually plays back more stably than a DAT machine. The fact that a dub can sound better than the original is certainly a tough concept to believe, but it is one key to understanding the strange phenomenom called Digital Audio.

It's unnerving to hear a dub that sounds sound different from the original, so I've performed some tests to try to see if jitter is accumulated. I think I've proved with reasonable satisfaction, that under most conditions jitter is not accumulated on multiple dubs, and that passing jittery sources through a storage medium (such as hard disk) results in a very non-jittery result (e.g., recorded CDR).

Here are two tests I have made (this is far from a complete list):

Test #1
I produced a 99th-generation versus 1st-generation audio test on Chesky Records' first Test CD. If jitter were accumulated on subsequent dubs, then the 99th generation would sound pretty bad, right? Well, most people listening to this CD can't tell the difference and there is room for doubt that there is a difference. It's pretty hard to refute a 99th generation listening test!

Test #2
I built a custom clock generator and put it in a DAT machine. On purpose, I increased the jitter of that clock generator to the point that a dubbing DAT machine almost could not lock to the signal from the jittery souce DAT. The sound coming out of the D/A converter of the dubbing DAT was entirely distorted, completely unlistenable. However, when played back, the dub had no audible distortion at all!

These are two scientifically-created proofs of an already well-understood digital "axiom", that the process of loading and storing digital data onto a storage medium effectively (or virtually) cancels the audible jitter coming in.

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Jitter påverkar alltså inte själva överföringen, utan snarare återgivningen.

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The first thing to know is that there are two kinds of jitter that relate to audio CDs. The usual meaning of "jitter" refers to a time-base error when digital samples are converted back to an analog signal; see the jitter article on http://www.digido.com/ for an explanation. The other form of "jitter" is used in the context of digital audio extraction from CDs. This kind of "jitter" causes extracted audio samples to be doubled-up or skipped entirely. (Some people will correctly point out that the latter usage is an abuse of the term "jitter", but we seem to be stuck with it.)

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