Re: What's the use of a 192 kHz sample rate?

Piergiorgio Sartor wrote:
> Steven Sullivan wrote:
> 
>> *Maybe* your friend was imagining things.
> 
> Exactly!
> I was close to say that *maybe* the Earth is flat.
> 
> With this kind of reasoning, everything is possible.
> 
> I tell you another story.
> 
> Once I met another guy, responsible of the quality
> in one audio CD factory.
> He told me that, looking for quality, they asked
> also audiophiles about what they think.
> It turned out that some people buy 2~3 copies of the
> same audio CD, they "test" it at home, and then keep
> the one that "sounds better".

This notion might be a hangover from a genuine issue in the early days 
of CDs. They used to struggle to make them, and many had pin prick holes 
through the metalisation. You could hold them up to the light, and 
easily see those holes. Wrapped in plastic in the shop you couldn't see 
these flaws. I knew an early adopter who would go through several copies 
until he found one that looked and played flawlessly.

> So, he was asking what could it be, are there any
> difference between CDs of different batches, maybe.
> They told him something about jitter, it seems
> different CDs can have different jitter.
> 
> He, then, took some high end CD player and measured
> all he could measure, including jitter, of different
> copies of the same CD(s).
> 
> He could not find anything strange, the high end CD
> player has FIFOs, which keep the jitter constant and
> minimum (low end is different story, but audiophiles
> use high end).

They all have FIFOs. The data isn't played directly from the disk. It is 
played from the ECC decode buffer. It is clocked from there to the DAC 
by a stable clock. It would take a pretty broken design to have so much 
phase noise in that clock that it produced significant jitter.

> In the end he could not figure it out what was the
> reason why different copies of the same CD should
> sound differently.
> 
> Next reply I'll tell you another of this stories.

Regards,
Steve