The receivers add a fair amount of jitter on their own. Either the photodetectors or the electronics used to amplify them are slow and noisy, the signal takes a long time to rise and there is a fair amount of noise on that ramp, which means the uncertainty in the threshold can cover a fair amount of time causing jitter.
There are ways to make this much better, the best of which is to have a multistage amplify and clamp system, this can detect the optical edge with very little added jitter, but costs way more than the "audio" receivers they currently sell. Toshiba certainly knows how to do this, some of their optical systems do it very well, but they don't offer that technology with the connector used for audio. 7 years ago I built a DAC with a TOSLINK receiver that has significantly lower jitter than what you can buy today, but Toshiba decided not to make those any more. (Probably because very few people were willing to pay the extra cost, it was something like 4X the price) Yes you CAN get extremely good performance on optical interconnects, the ones I deal with at work have about 10ps of jitter, but they cost several hundred dollars per channel, its hard to get that level of performance for 25 cents, which is about what the electronics in an audio TOSLINK receiver costs. If you boost it up to $2 worth of electronics you can get much better performance, but now the receiver costs $12 instead of $1.50. It seems there just is not a big enough market for $12 TOSLINK receivers. What I don't get is how come some enterprising people haven't started selling the improved optical receivers with the $2 of electronics for $100 a piece to the audiophile market. For people that drop $500 on a cable the extra $100 for a really good optical receiver should be a slam dunk. John S. -- JohnSwenson ------------------------------------------------------------------------ JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=90211 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
