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View Full Version : Sound quality varible digital out vs. fixed digital output



WK446
2005-07-29, 11:54
Hi all.
This is my first post, but I have been reading the various posts with enthusiasm and I am a self-professed audiophile.

I was wondering if forum members suggest using the fixed digital output or the variable digital output to get maximum sound quality with an external DAC?

Cheers,
Dennis

fuzzyT
2005-07-29, 12:04
WK446 wrote:

> I was wondering if forum members suggest using the fixed digital output
> or the variable digital output to get maximum sound quality with an
> external DAC?

Welcome.

Fixed.

Topic's been done to death, but the upshot is that for perfect
bit-fidelity, use Fixed.

But if SB remote volume control is a good feature for you then go ahead
and use it. Volume may ramp into inaudibility well before resolution
losses rear up.

--rt

WK446
2005-07-29, 12:11
Thanks RT...

Cheers,
Dennis

pfarrell
2005-07-29, 12:39
On Fri, 2005-07-29 at 15:04 -0400, ron thigpen wrote:
> > I was wondering if forum members suggest using the fixed digital output
> > or the variable digital output to get maximum sound quality with an
> > external DAC?
> Fixed.
> Topic's been done to death, but the upshot is that for perfect
> bit-fidelity, use Fixed.

Ron's right. Use fixed.
If you alter the volume, for perfection you would have
to redither the data. And that would start discussions
about which dithering algorithm to use, how we
could get the SBx2 to apply the right dither on the fly
and all sort of stuff that isn't worth getting into.

Use the volume knob on your preamp.

BTW, on my Classe integrated amp, I had to
change internal jumpers on my Benchmark DAC-1
as it was overdriving the Classe' input side.


--
Pat
http://www.pfarrell.com/music/slimserver/slimsoftware.html

WK446
2005-07-29, 16:16
Pat,

Were you referring to the balanced output jumpers on your DAC1? I was informed that 0dB was the best setting for sound quality.




BTW, on my Classe integrated amp, I had to
change internal jumpers on my Benchmark DAC-1
as it was overdriving the Classe' input side.


--
Pat
http://www.pfarrell.com/music/slimserver/slimsoftware.html

pfarrell
2005-07-29, 16:30
On Fri, 2005-07-29 at 16:16 -0700, WK446 wrote:
> pfarrell Wrote:
> > BTW, on my Classe integrated amp, I had to
> > change internal jumpers on my Benchmark DAC-1
> > as it was overdriving the Classe' input side.

> Were you referring to the balanced output jumpers on your DAC1? I was
> informed that 0dB was the best setting for sound quality.

I'm using balanced outputs, I have lots of XLR cables for my recording
studio. I don't remember if the jumpers control both balanced and RCA,
or just one or the other. I wacked 20dB off. Just checked the benchmark
site, they have the manual online, they call it
"XLR Output Attenuation Jumpers (P5, P6, P7 and P8)"

I did not use the ten turn attenuation pots.

Overdriving the preamp caused easily audible distortion.
Reducing it clearly improved my sound quality.

--
Pat
http://www.pfarrell.com/music/slimserver/slimsoftware.html

Yannzola
2005-07-29, 16:39
Use the volume knob on your preamp.


I'm considering putting together a new hifi rig, with the SB2 as the only source. I was hoping to bypass analog volume control altogether... relying instead on the SB2 digital volume control of the analog out via RCA. Of course, the trade off here involves dropped bits vs. the potential signal loss introduced by adding volume controls in the analog signal path. 99% of what I'll be listening to are 16bit Flacs. Will the 24bit digital volume control give me any headroom before modifying the signal? Or is the signal modified (re-aliased?) as soon as the digital volume is no longer fixed at 40?

Basically, I'm wondering which is better (less sonically degrading) given the choice: adjusting the volume digitally or adding some sort of analog volume control into the stream?

y.

inguz
2005-07-29, 17:10
...and for me, the remote control beats walking across the room to adjust volume even if there's a slight quality penalty.

. . . o O ( As long as I don't lose the remote )

pfarrell
2005-07-29, 18:05
On Fri, 2005-07-29 at 16:39 -0700, Yannzola wrote:
> Of course, the trade off here involves dropped bits vs. the
> potential signal loss introduced by the adding volume controls in the
> signal path.

You lose a bit every 6dB of attenuation you ask for.
You only get the theoretical 96dB signal to noise
ratio at wide open. When you cut it by 30dB, you
are talking about 11 bit signals.

> 24bit digital volume control give me any headroom before modifying the
> signal?

I'm not sure what you mean here. 24 bit has no more headroom.
The normal way to look at digital signals is that zero dbfs
is the max. (dB full scale). Signals max out at 0 dBfs, and
get smaller.

> Or is the signal modified (re-aliased?) as soon as the digital
> volume is no longer fixed at 40?

I don't know what you mean by re-aliased. Standard practice would
be to re-dither. Someone from SlimDev would have to comment
on what their algorithm does.

> Basically, I'm wondering which is better (less sonically degrading)
> given the choice: adjusting the volume digitally or adding some sort of
> analog volume control into the stream?

I think the answer depends on too many things, like the algorithm used
mentioned above. I bought my Classe years before I got my first
SqueezeBox. If I was starting over, I would consider skipping the
preamp completely and running the SqueezeBox directly into a pair
of monoblocks. If you later decided that you needed a preamp,
you can always add one.

--
Pat
http://www.pfarrell.com/music/slimserver/slimsoftware.html

Yannzola
2005-07-29, 18:55
I'm not sure what you mean here. 24 bit has no more headroom.
The normal way to look at digital signals is that zero dbfs
is the max. (dB full scale). Signals max out at 0 dBfs, and
get smaller.

It's only natural you don't know what I mean when I don't really know what I'm talking about. ;-)


I don't know what you mean by re-aliased. Standard practice would
be to re-dither. Someone from SlimDev would have to comment
on what their algorithm does.

Re-aliasing.... you know...uh... OK. See above. Basically, I was asking if <bad things> occured when the digital volume wasn't all the way to 40. uhhh... I think I should stick to using non-sense words when describing things I do not fully grok. It's only fair to make the extent of my ignorance obviously explicit.


I bought my Classe years before I got my first
SqueezeBox. If I was starting over, I would consider skipping the
preamp completely and running the SqueezeBox directly into a pair
of monoblocks. If you later decided that you needed a preamp,
you can always add one.

Aha! Yes! This is what I was really after. If you had to do it from scratch.... would you (in a single source situation) bypass the pre-amp and go directly to amplification, using the digital volume control of the SB2 for attenuation.

You =would= skip the pre-amp. Good answer... that saves me money!
Thanks pfarrell!

y.

pfarrell
2005-07-29, 19:08
On Fri, 2005-07-29 at 18:55 -0700, Yannzola wrote:
> > SqueezeBox. If I was starting over, I would consider skipping the
> > preamp completely and running the SqueezeBox directly into a pair
> > of monoblocks. If you later decided that you needed a preamp,
> > you can always add one.
>
> You =would= skip the pre-amp. Good answer... that saves me money!

The main reasons for trying this approach is:

1) it is cheaper
2) less things in the signal path is less things to mess with
the sound
3) if you decide you want a preamp later, get one. You haven't
lost anything.

With the money you save, you can spend more on the amp/speakers,
or buy more CDs, or take your SO out to dinner.

--
Pat
http://www.pfarrell.com/music/slimserver/slimsoftware.html

Mark.Bennett
2005-07-31, 07:56
On Fri, 2005-07-29 at 15:39 -0400, Pat Farrell wrote:
> BTW, on my Classe integrated amp, I had to
> change internal jumpers on my Benchmark DAC-1
> as it was overdriving the Classe' input side.

I had the same problem with my Meridian G02 Pre-Amp. I
think I only needed to take 10dB off though. I'm
using the balanced XLR's from the DAC-1, and the jumpers
definitely adjust the balanced outputs.

Hard to tell a significant sound quality difference
between using the variable outputs from the DAC
though.

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