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Sudhi Mukherjee
2005-02-08, 09:02
I would like to know if volume control in the squeeze box is done in the
analog or the digital domain. The reason I ask is that if I were to use an
external DAC for the digital output from the squeezebox, would I need a
volume control (such as a preamp/receiver) before I can hook it up to a
power amp. Thank you.

Sudhi

Aaron Zinck
2005-02-08, 09:37
You wouldn't have to--the digital out is variable (though it can be set to
be fixed)


"Sudhi Mukherjee" <sudhi_muk (AT) hotmail (DOT) com> wrote
in message news:BAY103-F394D149945F81FADBAE7E280740 (AT) phx (DOT) gbl...
> I would like to know if volume control in the squeeze box is done in the
> analog or the digital domain. The reason I ask is that if I were to use an
> external DAC for the digital output from the squeezebox, would I need a
> volume control (such as a preamp/receiver) before I can hook it up to a
> power amp. Thank you.
>
> Sudhi

Robin Bowes
2005-02-08, 11:38
Aaron Zinck wrote:
> "Sudhi Mukherjee" wrote in message
> news:BAY103-F394D149945F81FADBAE7E280740 (AT) phx (DOT) gbl...
>
>
>> I would like to know if volume control in the squeeze box is done
>> in the analog or the digital domain. The reason I ask is that if I
>> were to use an external DAC for the digital output from the
>> squeezebox, would I need a volume control (such as a
>> preamp/receiver) before I can hook it up to a power amp. Thank you.
>>
> You wouldn't have to--the digital out is variable (though it can be
> set to be fixed)

(Top-posting *and* quoting OP's email address fixed. Sheesh)

Variable digital output level may be convenient, but sound quality would
suffer.

In my view it would appear a little pointless to use an external DAC,
presumably for better sound quality, and then compromise quality by
reducing the digital level.

R.
--
http://robinbowes.com

Aaron Zinck
2005-02-08, 12:42
"Robin Bowes" wrote in message news:cub0rb$g9q$1 (AT) sea (DOT) gmane.org...
> Aaron Zinck wrote:
> > "Sudhi Mukherjee" wrote in message
> >
news:BAY103-F394D149945F81FADBAE7E280740 (AT) phx (DOT) gbl...
> >
> >
> >> I would like to know if volume control in the squeeze box is done
> >> in the analog or the digital domain. The reason I ask is that if I
> >> were to use an external DAC for the digital output from the
> >> squeezebox, would I need a volume control (such as a
> >> preamp/receiver) before I can hook it up to a power amp. Thank you.
> >>
> > You wouldn't have to--the digital out is variable (though it can be
> > set to be fixed)
>
> (Top-posting *and* quoting OP's email address fixed. Sheesh)
>
> Variable digital output level may be convenient, but sound quality would
> suffer.
>
> In my view it would appear a little pointless to use an external DAC,
> presumably for better sound quality, and then compromise quality by
> reducing the digital level.
>
> R.
> --
> http://robinbowes.com

Sorry to have caused any distress--I'm certainly a newbie to email lists and
am not familiar with all of the appropriate etiquette.

I've often heard the argument about the sound quality being compromised by
reducing the digital level (I don't actual do this--I have a preamp in the
mix for volume control on my setup) but I'm not 100% sure I understand why
this is claimed to be. Is it that a dac has a fixed noise floor (thus
resulting in a decreased signal to noise ratio when decoding a quiet signal)
while a preamp has a variable noise floor (thus a more-or-less constant
signal to noise ratio)? Or does the argument focus around something having
to do with how the digital information itself is affected as the volume is
raised/lowered?

Mark Bennett
2005-02-08, 13:11
On Tue, 2005-02-08 at 14:42 -0500, Aaron Zinck wrote:
> "Robin Bowes" wrote in message news:cub0rb$g9q$1 (AT) sea (DOT) gmane.org...
> > Aaron Zinck wrote:
> > > "Sudhi Mukherjee" wrote in message
> > >
> news:BAY103-F394D149945F81FADBAE7E280740 (AT) phx (DOT) gbl...
> > >
> > >
> > >> I would like to know if volume control in the squeeze box is done
> > >> in the analog or the digital domain. The reason I ask is that if I
> > >> were to use an external DAC for the digital output from the
> > >> squeezebox, would I need a volume control (such as a
> > >> preamp/receiver) before I can hook it up to a power amp. Thank you.
> > >>
> > > You wouldn't have to--the digital out is variable (though it can be
> > > set to be fixed)
> >
> > (Top-posting *and* quoting OP's email address fixed. Sheesh)
> >
> > Variable digital output level may be convenient, but sound quality would
> > suffer.
> >
> > In my view it would appear a little pointless to use an external DAC,
> > presumably for better sound quality, and then compromise quality by
> > reducing the digital level.
> >
> > R.
> > --
> > http://robinbowes.com
>
> Sorry to have caused any distress--I'm certainly a newbie to email lists and
> am not familiar with all of the appropriate etiquette.
>
> I've often heard the argument about the sound quality being compromised by
> reducing the digital level (I don't actual do this--I have a preamp in the
> mix for volume control on my setup) but I'm not 100% sure I understand why
> this is claimed to be. Is it that a dac has a fixed noise floor (thus
> resulting in a decreased signal to noise ratio when decoding a quiet signal)
> while a preamp has a variable noise floor (thus a more-or-less constant
> signal to noise ratio)? Or does the argument focus around something having
> to do with how the digital information itself is affected as the volume is
> raised/lowered?

The sound quality argument for digital volume control is focused
around resolution.

On an analogue system, as you reduce the volume the low-level detail
in the signal also scales down, but is (theoretically) faithfully
reproduced.

If you want to cover a reasonable volume range with digital volume
control then you inevitably end up losing bits, which means that
the low-level detail doesn't just get quieter, it actually
disappears.

Of course, whether this low-level detail can actually be heard or
not is open to discussion amongst the audiophiles.

In basic functionality, the squeezebox can do digital gain through
an external DAC, so analogue gain control (i.e. a pre-amp) is not
strictly required. I would recommend trying to use the digital
gain into a DAC/Power Amp combo, and see if it meets your
quality requirements, particularly at low volumes. If it is OK
then you're happy. If not, then you might have to consider adding
some form of analogue volume control.

--
"The biggest problem encountered while trying to design a system that
was completely foolproof, was, that people tended to underestimate the
ingenuity of complete fools." (Douglas Adams)

Aaron Zinck
2005-02-08, 13:50
Thanks for the explanation! I'm surprised I didn't consider this given the
absolutely fixed limits on digital audio's dynamic range.

Robin Bowes
2005-02-08, 13:56
Aaron Zinck wrote:
> Sorry to have caused any distress--I'm certainly a newbie to email lists and
> am not familiar with all of the appropriate etiquette.

Don't worry - I had a bad day today :)

> I've often heard the argument about the sound quality being compromised by
> reducing the digital level (I don't actual do this--I have a preamp in the
> mix for volume control on my setup) but I'm not 100% sure I understand why
> this is claimed to be. Is it that a dac has a fixed noise floor (thus
> resulting in a decreased signal to noise ratio when decoding a quiet signal)
> while a preamp has a variable noise floor (thus a more-or-less constant
> signal to noise ratio)? Or does the argument focus around something having
> to do with how the digital information itself is affected as the volume is
> raised/lowered?

Option (b).

When you reduce digital volume you lose information and create distortion.

For example, the digital samples are coded as 16-bit information. That's:

1111111111111111

Each sample can have one of 2**16 values (there's a sign bit involved as
well, but keeping things simple for the purposes of this example).
That's 65536 different values;

If you (say) half the volume digitally, the full-scale value doesn't
change but the maximum level is now 65536/2 = 32768. So, those 65536
values are reduced to 32768. For example, 65536 -> 32768. But what about
65535? Does that reduce to 32767 or 32768 as well?

Basically, you've lost 50% of the amplitude information.

This loss of information manifests itself as distortion. The lower you
go, the more the distortion.

R.
--
http://robinbowes.com