RE: OT: Optical and coaxial digital outputs for PCM, Dolby Digital, DTS and MPEG

["Mark Harrison" <Mark.Harrison@xxxxxxx>]

OK, here goes ;-)


When you're talking about an integrated CD/DVD player, then you have a
whole bunch of options for ensuring low jitter and sync that stop
becoming available the moment you want to squirt a data stream onto a
SP/DIF or even worse, a TOSLINK bus.

I will ignore any other sorts of output circuitry you might use, from
AES/EBU upwards through a whole bunch of proprietary stuff on the basis
that "sod all domestic stuff has it".

On that basis it is possible that the internal DAC is working from a
better signal than an external DAC on the same player. It's not that the
DAC is "putting back" something, it's that it's worked out a way
to
never lose it in the first place :-)


On the question of "battleship" transports vs. cheap ones with
massive
solid state buffers, I completely agree with you.

One of the problems with most CD players / DACs is that, rather than
upshifting the frequency from some common feed, they tend to both
generate their own idea of 44.1kz from crystals. You only need to be a
fraction of a % out to generate many bits of underrun/overrun errors per
second, and make "ludicrously big" both the required buffer size
downstream of the link (ie at the DAC), but also the "latency
time" of
starting playing (ie how long you needed to run music to partfill the
buffer before you started playing.)

This is particularly noticeable when you start reading your data from
something that isn't an optical disk, and why I like ripping DVDs onto
hard disk. Buffer underruns just go away, because everything's provided
as needed, WITH "big" buffers in main RAM.

However, once again this is a question of what is possible on internal
transports rather than external ones. On an integrated system, you can
use your buffer size utilisation to speed up or slow down the rate at
which the transport feeds you. On a separate Transport/DAC system, using
standard connections, you can't, 'cos the feeds fundamentally one way.


However, AND THIS IS IMPORTANT, _and_ the area on which both of us agree
;-)...

.... The best way to tell whether one manufacturer's product is
"better"
than anothers is to LISTEN TO IT IN YOUR OWN SYSTEM.

.... This is why I always suggest people buy from BADA dealers since, if
you change your mind within 7 days, they'll give you your money back for
no reason beyond "sorry - didn't sound right once I got it home - must
be something to do with the rest of my system."

Mark Harrison
Head of Systems, eKingfisher


-----Original Message-----
From: Phil Harris [mailto:phillip.harris1@xxxxxxx]
Sent: 17 December 2001 14:53
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] OT: Optical and coaxial digital outputs for PCM,
Dolby Digital, DTS and MPEG



> Micromega are generally regarded as having put their effort
> into a great DAC and analogue output stage and a poorer
> transport. As such, if you're listening to it through a good
> quality set of analogue amps, it will really sing.
>
> If however, you're bypassing the DAC and analogue stages, and
> therefore using someone else's, then you're only using the
> poorer part of your CD player.

This implies that the DACs are "putting back" something that is
missing
in the original bitstream that is being passed to them. Therefore the
logical conclusion os this is surely to imply that the DACs are not
transparent and are imposing their own sonic character which in my books
would make them a bad DAC - no?

I love these discussions on good and bad digital transports ... Years
ago Meridian were making hugely heavy and battleship build transports
and I was having a heated debate with a mate that what they should do is
use a PC CD ROM drive and just buffer the hell out of the data if what
they were concerned about was jitter ... Now that supplies of the
"built
like a brick shithouse" Philips transports that they used to use have
dried up what are they doing? Using PC CD/DVD drives with buffers to
reclock the data!

Even their top of the line 800 series DVD player uses a standard DVD ROM
transport!

Remember : If it isn't pulled off the disc at the very start of the
chain then you can't hope to add it back in later...

Phil



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