(08-08-2018, 02:06 AM)Jacques92 a écrit : http://www.tnt-audio.com/clinica/jitter1_e.html
http://www.tnt-audio.com/clinica/jitter2_e.html
http://www.tnt-audio.com/clinica/jitter3_e.html
+ bibliographie référencée dans ces pages web.
Merci. C'est probablement l'article le plus clair sans être trivial que j'ai lu sur le sujet.
Pour moi, le passage le plus interessant est ici:
Effects of Jitter in Audio
[i]Far less clear are the effects of jitter on human hearing, and its tolerability.
Studies [6] seem to demonstrate that the lowest sampling jitter amount that makes a sensible difference is 10ns RMS with a 17KHz pure tone; with music the minimum amount seems to be 20ns RMS
In my personal experience, and I would dare say in common understanding, there is a huge difference between the sound of low and high jitter systems. When the jitter amount is very high, as in very low cost CD players (2ns), the result is somewhat similar to wow and flutter, the well known problem that affected typically compact cassettes (and in a far less evident way turntables) and was caused by the non perfectly constant speed of the tape: the effect is similar, but here the variations have a far higher frequency and for this reasons are less easy to perceive but equally annoying. Very often in these cases the rhythmic message, the pace of the most complicated musical plots is partially or completely lost, music is dull, scarcely involving and apparently meaningless, it does not make any sense. Apart for harshness, the typical "digital" sound, in a word.
In lower amounts, the effect above is difficult to perceive, but jitter is still able to cause problems: reduction of the soundstage width and/or depth, lack of focus, sometimes a veil on the music. These effects are however far more difficult to trace back to jitter, as can be caused by many other factors.
I also remember someone reporting to have obtained a very pleasant sound at a certain point while tweaking his own player, just to understand to his own surprise that he had been injecting by mistake high level 600Hz jitter into the clock... The sound was reported as soft compared with the original player, so it is possible that jitter added some kind of veil that reduced the "digitality" of sound.
I have recently tested the Weiss Medea, one of the lowest jitter DAC existing, and the precision and detail are absolutely outstanding. I cannot be completely sure, but I think that low jitter has a part in this.
[6] Eric Benjamin and Benjamin Gannon - "Theoretical and Audible Effects of Jitter on Digital Audio Quality", AES, 1998.
Contrairement au reste de l'article, ici l'auteur fait appel à des impressions, des lieux communs (the typical "digital" sound) et non à des faits. Il le reconnait d'ailleurs en partie lui même. Par ailleurs, le Weiss Medea date de 2003, donc l'article a 15 ans.