What is the benefit of a good transport?


I'm trying to understand the role of the transport - i.e., what does it need to do and what differentiates one from another? How old is too old when it comes to used transports? I know it reads the disc, but I don't really get how one is different than another. Thanks for any advice.
mainer8
I don't know exactly why transports sound different, but they do! Alright, alright, it's about 0's and 1's but... I think it's about jitter, don't you think? So in theory the transport with the less jitter is the superior one, I suppose... Have you heard a good sounding jitter troubled transport? In that case, just forget my preassumptions, I'm not a digital guru.

Chris
Jitter is the biggie. In non technical terms, it is 0's and 1's, but if the timing of their arrival to the DAC is off or not even or smooth, etc, then the DAC is going to have to work extra hard to turn those messy numbers into music. And down goes the sound quality.
So if it is about jitter is that something that new technology has improved upon or is an old (say early 90s), high quality transport more or less as good as any newer transport?
It is my understanding that jitter can be dealt with at the transport level, the DAC level or both for that matter. A signal is passed, along with the ones and zeros, to the DAC and if the DAC is designed to reclock the signal, jitter is dealt with.
As a non digital expert (not an engineer), how would a DAC know that the signal it receives needs to be re-clocked? I can imagine a transport doing that, since it is reading the source material.