Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it.

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Or get the clock out of the PC

Posted by Jim F. (A) on January 12, 2009 at 01:18:56

In Reply to: RE: Bel Canto DAC3 vs Cullen Modified PS DL III vs ? posted by Dawnrazor on January 11, 2009 at 00:15:23:

> > The end goal is that my music server system must sound
> > at least as good as the Accuphase DP-65v CDP that I have
> > been using for the past several years.
>
> There are several people who say that SOFTWARE makes a
> big difference (even on a mac), and that to get the most
> out of you computer you need to use different programs than
> the free ones.

You know, assuming that the computer and the player software
get the data off the hard drive and into the DAC (wherever it
may be) without actual bit errors, or other gross anomalies
like dropouts, clicks & pops, or other hiccups due to buffer
underruns and the like, then the likeliest source of any
sonic differences due to load placed on the processor by
player software, etc., would seem to have to be jitter related.

There is one solution to this -- get the clock out of the
computer! A DAC with a word clock output and a sound card
with a word clock input will allow you to do this.

Now, there aren't many consumer (read "audiophile") DACs
with word-clock outputs -- the $7500 Esoteric (by Teac)
D-05 comes to mind -- but there are plenty of (comparatively
reasonably priced) pro A/D-D/A converters that do have
word-clock outputs, such as the Apogee Rosetta 200. There
are also a few (pro) sound cards that have word-clock inputs,
such as the Lynx cards.

If the card is "slaved" to the DAC's local clock, then
it seems likely that differences between Foobar and "memory
players" using highly "tuned" PCs and the like will disappear.

I'm using such an arrangement myself, though I don't
have a card with a word-clock input as such. My E-MU 1212
can sync to an external clock source, but only via one
of its data-carrying inputs (ADAT, AES, etc.) So I "trick"
it into accepting my DAC's local clock in the following way.
(All of my playback is at 192 kHz.)

My "computer DAC" is an Apogee Rosetta 200 (a "low-end", as such
things go, pro A/D-D/A converter). I send its word-clock
output to the word-clock input of an RME ADI-192DD
digital format converter. I also send the RME a stream
of "digital silence" from another idling A/D converter.
The RME has sample-rate converter that takes the Rosetta's clock as
its output sample rate, and generates an ADAT output (consisting of
digital silence, at 192 kHz) for the E-MU, perfectly
synced to the Apogee Rosetta's clock. The E-MU is slaved
to that ADAT input. (I also have a
**second** RME, also slaved to the Rosetta's clock,
that's receiving the ADAT **output** from the
E-MU, this time containing the music that I'm
listening to, and which 1) converts the 192 kHz
ADAT/S-Mux4 into dual-wire AES for the Rosetta
(because the Rosetta can only accept 176 or 192
via dual-wire AES), and also sends the ADAT/S-Mux4
on to several other systems (that are fed from
Apogee Big Bens, all on one big optical "bus"
connected with 50 foot Hosa glass Toslink cables).

Note that in this arrangement: 1) the master clock
is in the Rosetta -- it's a high-quality, stable
clock, and it is also local to the DAC
and 2) the sound equipment is electrically isolated
from the computer (the E-MU's ADAT input and output
happens via Toslink optical cables).

It sounds pretty good, and while I have not spent any time
comparing playback software (I use Foobar -- either
0.9.5 or 0.8.3, with their respective ASIO DLLs),
I have no reason to believe that the "brand" of player
software could have any possible effect on this arrangement
(unless, of course, I were getting glitches, which I'm
not. My music is on an external disk drive in a
Firewire enclosure, and I keep it defragmented. It's
also a 1TB drive, with a pretty big buffer -- what
are they, 16 MB these days? And Foobar seems to do
a perfect job of decoding WavPack lossless on the fly.)

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