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Simon Turner
2004-02-26, 02:12
A few people (including me) are talking about buying rather expensive Dacs
to achieve high end audio using PC's, Flacs and the Squeezebox.

Is this realistic bearing in mind that we are replacing a dedicated CD
player with a hard drive. Surely all the drawbacks that good CD players
strive so hard to overcome are inherant (in spades) on a hard drive, i.e
jitter, cheap power supply etc.

In addition is it certain that the streaming process itself will not degrade
the sound, or even that the digital-out on the Squeezebox outputs exactly
the stream it receives?

Regards,
Simon Turner
Brighton UK

Pat Farrell
2004-02-26, 10:06
At 04:12 AM 2/26/2004, Simon Turner wrote:
>Is this realistic bearing in mind that we are replacing a dedicated CD
>player with a hard drive. Surely all the drawbacks that good CD players
>strive so hard to overcome are inherant (in spades) on a hard drive, i.e
>jitter, cheap power supply etc.

A lot of "jitter" is just a buzzword used by the audiophile community to
sell very expensive gear. Jitter is properly a difference in clocking between
digital and analog signals.

Digital signals do not have jitter. Convertors have jitter.

In any CD player, there are two conversions. Two places for jitter.
First, the analog pits on the CD are read and converted to digital PCM.
Second, the PCM is converted thru the DAC to analog. Most audiophile
talk is about the second. Hardly anyone talks about the first, but when we
extracted data from 40,000 CDs, we found that different drives got
different bits from the same CD. Don't know if it was jitter or error
correction,
or cheapness, but there was a difference.

In a SqueezeBox world, the first possible jitter is gone. You use your favorite
rip/extraction software to read the digital audio and put it as a WAV, MP3,
ogg,
flac, etc.

The second is a possible concern with the SqueeseBox world, but
an external DAC resolves it. The Benchmark site has good information on
what they do to control the effects of jitter in their DAC-1.

Cheap power supplies? like the wallwart that comes with a SqueezeBox?
Actually, with an external DAC, the power inside the SqueezeBox has
zero impact on the sound. But be fair, the whole SqueezeBox costs less
than the power cable that audiophiles obsess about.

To my view, the beauty of a SqueezeBox system is to remove all
attractiveness of the audiophile $5000 "cd transport"
The $300 Sbx probably has a $20 DAC, but I can replace it with one
costing $200, $1000, or even $20,000 if I want to, and not have to
touch my CDs or server. Very cool.

>In addition is it certain that the streaming process itself will not degrade
>the sound, or even that the digital-out on the Squeezebox outputs exactly
>the stream it receives?

I can't talk about how bit accurate the SqueezeBox outputs are, but
streaming is
just data transfer. Using TCP/IP, it is error protected and ordered.
It is just a pipe, as long as there are no big drop outs.

The beauty of digital audio is that it is digital, it flat works or does not.
No room for subtle degradations.

The point in getting a better DAC is that the DAC process has huge
room for non-linearities. Both the DAC and ADC sides can make clear
and audible differences.

Pat

p.s. I've noticed that the traffic volume on this list is higher than
advertized.
And that there are several kinds of different threads (how come my server
doesn't
work, how do I do X, how to make it sound better, techniques to create
a music farm, etc.) At some point, it will make sense to have separate
lists for
different types of discussions. Anybody got an idea as to when that split
should occur?

alexd
2004-02-26, 13:07
On Thu, 2004-02-26 at 12:06 -0500, Pat Farrell wrote:

> p.s. I've noticed that the traffic volume on this list is higher than
> advertized.
> And that there are several kinds of different threads (how come my
> server doesn't
> work, how do I do X, how to make it sound better, techniques to create
> a music farm, etc.) At some point, it will make sense to have separate
> lists for
> different types of discussions. Anybody got an idea as to when that
> split
> should occur?

When anybody with a question can pick the right list without anybody
else telling them that said question belongs on a different list. In
other words, never. Accurate thread Subject:s would be helpful, enabling
one to easily ignore irrelevant threads.

alexd
--
http://alexd.mine.nu

kdf
2004-02-26, 13:48
Quoting alexd <troff-news (AT) blueyonder (DOT) co.uk>:

> On Thu, 2004-02-26 at 12:06 -0500, Pat Farrell wrote:
>
> > p.s. I've noticed that the traffic volume on this list is higher than
> > advertized.
> > And that there are several kinds of different threads (how come my
> > server doesn't
> > work, how do I do X, how to make it sound better, techniques to create
> > a music farm, etc.) At some point, it will make sense to have separate
> > lists for
> > different types of discussions. Anybody got an idea as to when that
> > split
> > should occur?
>
> When anybody with a question can pick the right list without anybody
> else telling them that said question belongs on a different list. In
> other words, never. Accurate thread Subject:s would be helpful, enabling
> one to easily ignore irrelevant threads.
>
> alexd

My feelings on this is really that the advertising should change. It has said
5-10 messages/day since I've been a user. This goes back to when this was on
yahoo groups and it was still well over 5 messages a day. Sean, Dean, Kevin,
Patrick...yer gaining in success and profile, why not admit it ;)

-kdf

seanadams
2004-02-26, 14:39
Fixed.


On Feb 26, 2004, at 12:48 PM, kdf wrote:

> Quoting alexd <troff-news (AT) blueyonder (DOT) co.uk>:
>
>> On Thu, 2004-02-26 at 12:06 -0500, Pat Farrell wrote:
>>
>>> p.s. I've noticed that the traffic volume on this list is higher than
>>> advertized.
>>> And that there are several kinds of different threads (how come my
>>> server doesn't
>>> work, how do I do X, how to make it sound better, techniques to
>>> create
>>> a music farm, etc.) At some point, it will make sense to have
>>> separate
>>> lists for
>>> different types of discussions. Anybody got an idea as to when that
>>> split
>>> should occur?
>>
>> When anybody with a question can pick the right list without anybody
>> else telling them that said question belongs on a different list. In
>> other words, never. Accurate thread Subject:s would be helpful,
>> enabling
>> one to easily ignore irrelevant threads.
>>
>> alexd
>
> My feelings on this is really that the advertising should change. It
> has said
> 5-10 messages/day since I've been a user. This goes back to when this
> was on
> yahoo groups and it was still well over 5 messages a day. Sean, Dean,
> Kevin,
> Patrick...yer gaining in success and profile, why not admit it ;)
>
> -kdf
>

Mark Bennett
2004-02-26, 15:11
Pat Farrell wrote:

> At 04:12 AM 2/26/2004, Simon Turner wrote:
>
> To my view, the beauty of a SqueezeBox system is to remove all
> attractiveness of the audiophile $5000 "cd transport"
> The $300 Sbx probably has a $20 DAC, but I can replace it with one
> costing $200, $1000, or even $20,000 if I want to, and not have to
> touch my CDs or server. Very cool.

This is exactly my position and I can see no reason why it shouldn't
be true.

>> In addition is it certain that the streaming process itself will not
>> degrade
>> the sound, or even that the digital-out on the Squeezebox outputs exactly
>> the stream it receives?
>
>
> I can't talk about how bit accurate the SqueezeBox outputs are, but
> streaming is
> just data transfer. Using TCP/IP, it is error protected and ordered.
> It is just a pipe, as long as there are no big drop outs.

Completely seconded on the network front. If this wasn't true then
computer networks as we know them would never work, and they
clearly do.

I also can't believe that the squeezebox or server is corrupting
the data - if it is then it's pretty subtle. It would be very
interesting to capture the digital stream coming out of the
squeezebox and then comparing it with the original. As long as
you're using WAV as the source and get the data alignment right
it really should be identical.

This is theoretically possible if someone has a PC with S/PDIF
in. Unfortunately I do not, although I'll add it to the spec
of my intended SlimServer machine to allow me to find out.

> The beauty of digital audio is that it is digital, it flat works or does
> not.
> No room for subtle degradations.

I'm not so sure I agree with this statement in this context.
In absolute terms you're completely right, but this is different.

The problem with CD player's is that they do occasionally read
the disc wrongly, and when the error correction is overloaded
they send out bad information. This damages the works/doesn't
work argument, because a few bits here and there wrong in the
data stream, which the mechanism interpolates to fill in for,
would be very hard, if not impossible, to detect subjectively.
As a whole I would expect them to appear as a subtle degradation.

The really old CD players used to indicate when the error
correction failed to correct errors, most players now hide that
information.

I suspect that in most cases the uncorrected error rate is pretty
low, if not zero, but I wouldn't like to put money on it.

The squeezebox really should have zero errors all the time, since
hard disks and computer networks have so much error correction
built in that it isn't likely to happen. If you get glitches on
the squeezebox it's probably going to be because the buffer empties
than any other reason.

Pat Farrell
2004-02-26, 19:10
At 05:11 PM 2/26/2004, Mark Bennett wrote:
>Pat Farrell wrote:
>>The beauty of digital audio is that it is digital, it flat works or does not.
>>No room for subtle degradations.
>I'm not so sure I agree with this statement in this context.
>In absolute terms you're completely right, but this is different.

No, it really isn't. :-)
Actually I think we are in agreement here.

>The problem with CD player's is that they do occasionally read
>the disc wrongly, and when the error correction is overloaded
>they send out bad information. This damages the works/doesn't
>work argument, because a few bits here and there wrong in the
>data stream, which the mechanism interpolates to fill in for,
>would be very hard, if not impossible, to detect subjectively.
>As a whole I would expect them to appear as a subtle degradation.

Correct. Since Red Book audio is read as analog pits, there is
plenty of room for the reading/extracting process to go wrong.
And the specs have assorted error correction techniques, and
finally some "fake the last signal" stuff to avoid silence.

And PC readers vary in quality a lot. The cheap ones do not
extract reliably. I use the TDK Velo ones, which are more expensive
but a lot more accurate. It is next to impossible to find out what
the real error rate is, some of the errors are caught and fixed in
the drive circuitry before it gets out to any real part of the CD player.
The errors have to be pretty massive before the main player
error fixup routines are called.

It might be cheaper to buy new CDs for the few that won't read
than to worry about it.

>I suspect that in most cases the uncorrected error rate is pretty
>low, if not zero, but I wouldn't like to put money on it.

It can be very high. Depends on the CD drive, the media,
surface grease, dirt, etc. It is common for two drives to extract
different files from a single CD.

>The squeezebox really should have zero errors all the time, since
>hard disks and computer networks have so much error correction
>built in that it isn't likely to happen. If you get glitches on
>the squeezebox it's probably going to be because the buffer empties
>than any other reason.

Again, this is really a separate issue.
Once the data is properly extracted ("ripped") then
you can transfer it all you want. The Sqbx will only
glitch if it is not fed fast enough.

A suitable network should more than keep an DAC happy.
And if not, you can replace hubs with switches, which are nearly
as cheap. Red Book audio only needs 150kB/s. Which is trivial
on any decent network. Even 96/24 stereo only needs about
four times that, still trivial.

Pat

Bhavesh Patel
2004-02-26, 19:52
I use an M-Audio Transit USB outboard DAC (around $80 US) and the sound
quality coming out of it is simply phenomenal. I've had relatively
higher end setups in the past (Adcom GCD-600 CD player, Adcom Preamp,
Bi-Amped speakers (Adcom amps), quality interconnects, proper speaker
placement, etc), in addition to Naim, Arcam, and some others, and this
easily rivals the best I've had. Most importantly, the clarity of the
music has been awesome. I am hearing things that I never heard before,
understanding words that I never understood before, and hearing a wider
stage with good depth.

Regards,

Bhavesh


On Feb 26, 2004, at 3:12 AM, Simon Turner wrote:

> A few people (including me) are talking about buying rather expensive
> Dacs
> to achieve high end audio using PC's, Flacs and the Squeezebox.
>
> Is this realistic bearing in mind that we are replacing a dedicated CD
> player with a hard drive. Surely all the drawbacks that good CD players
> strive so hard to overcome are inherant (in spades) on a hard drive,
> i.e
> jitter, cheap power supply etc.
>
> In addition is it certain that the streaming process itself will not
> degrade
> the sound, or even that the digital-out on the Squeezebox outputs
> exactly
> the stream it receives?
>
> Regards,
> Simon Turner
> Brighton UK
>
>
>

Pat Farrell
2004-02-27, 10:00
At 04:49 AM 2/27/2004, Simon Turner wrote:
>I just want to summarise this thread.
>It seems to me that it is very likely that if CDs are ripped to Flac using
>Exact Audio Copy in sercure mode and a good DAC is added to the digital
>output of the Squeezebox then there is no real reason why the analogue
>signl to a hifi amp should not be more accurate than that obtained from a
>very expensive CD Player.
> Hmmm... better sell my CD player quick....

Correct, except you probably don't want to talk about "more accurate" in this
context. Better to think in terms of "exactly the same as" rather than "more"

And of course, accuracy is not really a goal anywhere in music.
Recording engineers select between microphones to make the music
sound "right" and to give it the proper emotional impact. If you check
the professional audio recording world, there are long discussions
about the coloring of this microphone, or preamp, or monitor. Let alone
recording studio, or concert hall acoustic signature.

Pat