Quote:
Originally Posted by
BIslander 
Aren't 2 & 3 part of the same clock issue? Now, please complete your explanation. How do the potential clocking and jitter problems produce the kinds of inferior audio outputs being described in this thread?
They are related, but not the same. What I am saying is jitter is inevitable without a master clock (and these get EXPENSIVE as any studio owner knows). An AVR must always syncronize to an external sources clock when fed a digital PCM stream because no two clocks can ever be independently syncronized. Inexpensive clocks (like the ones in our players, and even our AVRs) will always have jitter. This means that even though the samples are coming out in a sequential stream the period which should be fixed and constant is slightly variable based on clock error and errors as a result of the transition medium. Jitter can come from the pickup mechanism in the case of raw PCM stored on a disc, and it can and is introduced in the transfer (through the cable). Since the stream is coming through PCM the receiver or DAC must lock to the source clock through a Phase Loop Lock (PLL) which will also introduce the potential for jitter. Since the period of the samples get's skewed as a result the resulting analog waveform will have distortion when the samples are reassembled. Since it occurs at the sample level a loss of high frequency resolution is the most audible result.
Audio that is bitstreamed is basically contained in a wrapper or package (the bitstream itself). PCM audio is not extracted until it reaches the decoder which (if it is located within the AVR) is the first place new jitter can be introduced (jitter introduced during recording is there forever in the audio). Since this is happening in the AVR with bitstream you will eliminate the potential for jitter to be introduced by the source player, the cable or transmission medium, and the external PLL lock. Inevitable there will be jitter introduced within the AVR system, but the logic here is that it will be a couple of orders of magnitude less, and since it is accumulative the effects will be far less.
Jitter is the enemy of a digital audio system and unless you have a high quality external master clock you will always have it to some degree (and even with the master clock to be honest).
As far as the difference between bitstream and PCM on my ONkyo 805, I'd venture to say something else is happening too. Audyssey is still active during LPCM and I did another comparison today. LPCM sound compressed and cruchy by comparison to bitstream. Almost distorted. Bitstream is clearly superior and it isn't a matter of loudness.
Again, if you're wondering I suggest you try it. Too many people agree there is a difference for it to be purely the placebo effect.
