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| quote: | Originally posted by alanzo
Well, I know what jitter is, if that helps the explanation. |
To expand on what kit said, when your soundcard takes "snapshots" of the signal 44,100 times a second (for arguments sake) the soundcard uses a timing mechanism to tell itself exactly when to take those samples of the signal. Now even incredibly small variations in timing (nanoseconds) can make a difference in accuracy of the signal becuase the samples have to be taken so many times a second. So, if you think of one milisecond = 1,000th of a second = 441 samples, you can see how even tiny innacuracies in timing will affect the accuracy of your soundcard, and therefore the sonic quality.
In studio systems where you have several different units all synced, often with their own clock references, those tiny variations (jitter) all add up and become a real problem. If each one is off by a tiny amount, then effectively they could be all relating to the same signal at different time intervals, which can cuase all sorts of artifacts, phasing and colouration issues.
So you use a master clock reference to feed the various units that all have to deal with the same audio signal, so effectively they are all on the same page at the same time.
Jitter is also more of an issue when using various sample rates at the same time. i.e. in film, the score might all be recorded at 44.1k but when you're printing the mix that will go on to a rig that 48k film standard, so having the bigben which can operate and feed at different rates simultaneously is a huge benefit.
To elaborate: Have you ever wondered why, if you get a camcorder and record a TV or computer monitor, you get thse horizontal moving lines or can see the screen refreshing? it's a similar thing - the capture rate of the camcorder is at a different rate of refresh to the screen. But when you see screens on in the background on TV broacasts such as the news etc, they don't do that. That's becuase they use a house sync to make sure everything is in sync with each other.
With small systems, such has home recording studios, an external clock is little benefit, becuase there are few links in the chain ans not much converting done (i.e. just in and out once), so the built in clocks on most cards are decent enough that jitter is not so much of an issue. Also, the higher the samples rate the more need there is for stable clocking, but as EDM producers, we hardly even do it.
RME interfaces have some of the best internal clocks and apogee are good too. Motu are decent, but do benefit from the BLA upgrade mainly becuase of the improved clock. Protools actually have quite shitty clocks considering they so expensive interfaces and that you often are linking them together.
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