S/PDIF?

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MZ - 07 Apr 2004 18:39 GMT

So I was thinking of getting a line driver to interface between my computer
and amplifiers, because the sound card output is rather low and, on my sub
amp at least, the gain is at the max (and I could afford to go a little
higher with it). However, I evidently have an S/PDIF output on this
computer, so I'm wondering if there's a decent, cost-effective S/PDIF
solution. I know nothing about S/PDIF. How on earth does the volume
control work for such a protocol?

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Brian - 08 Apr 2004 06:19 GMT

I've used S/PDIF with my home audio. I connected the digital signal
from my PC's sound card S/PDIF, using a 30 ft cable, to a preamp in my
livingroom. The preamp accepts the S/PDIF signal (digital input).

I can control the volume both at the PC and/or at the pre-amp.

You probably could do the same with yor car stereo.

> So I was thinking of getting a line driver to interface between my computer
> and amplifiers, because the sound card output is rather low and, on my sub
[quoted text clipped - 3 lines]
> solution. I know nothing about S/PDIF. How on earth does the volume
> control work for such a protocol?

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Matt Bhame - 08 Apr 2004 16:11 GMT

>> So I was thinking of getting a line driver to interface between my
>> computer and amplifiers, because the sound card output is rather low
[quoted text clipped - 3 lines]
>> cost-effective S/PDIF solution. I know nothing about S/PDIF. How on
>> earth does the volume control work for such a protocol?

To my knowledge SPDIF is 'digital' audio, using a coaxial medium - because
of which it is considered, by some, to not be truly 'digital' as they
consider Optical truly 'digital'...ANYWHO...

If your PC can control the 'volume' of your sound card's SPDIF output that
is somewhat unnerving. SPDIF Out from a PC should primarily be an
unamplified constant level output - like going to an inexpensive SOHO 5.1
system - similar to a Digital Optical Out. There is NO volume control for
Digital Optical Out because it's sending pulses of light emulating 0 bits
and 1 bits. Perhaps there is a volume emulation built-into its protocol
but bottom line, from my understanding, is it's either sending data or it's
not.

And I would say it's safe to assume that anything receiving the signal from
a PC's SPDIF Out would HAVE to be amplified, thus my concern with the fact
you CAN control its volume. I would also worry if your PC Sound card has
some sort of garbage amplification on this line as well, which I wouldn't
want either. What Sound Card is it?

I'm interested to know now for my own understanding. If it's 'integrated
sound' - ie - built-in to the motherboard odds are very strong it's not a
very good sound card at all. SoundBlaster's Audigy 2 or M-Audio has
greatly improved PC's sound quality using true 24bit D/A converters, etc.
I *think* M-Audio's card has a purer sound but lacks many features better-
suited to a PC (gaming) that the Audigy has.

Now, don't take MY word for gospel - this is just what my understanding is
but I can't posture myself to really *know*.

Matt

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MZ - 08 Apr 2004 18:44 GMT

> >> So I was thinking of getting a line driver to interface between my
> >> computer and amplifiers, because the sound card output is rather low
[quoted text clipped - 7 lines]
> of which it is considered, by some, to not be truly 'digital' as they
> consider Optical truly 'digital'...ANYWHO...

But the "digital" designation has only to do with the information and not
the media through which it's transmitted. In any case, it doesn't matter a
whole lot to me anyway. I'm not entirely sure that the difference between
this sound card and a top quality sound card will be noticable. The digital
protocol isn't exactly my concern, as much as it is simply bypassing the
sound card's analog output, which I have not personally tested (and I can't
find it up on Arny Krueger's site either!).

> If your PC can control the 'volume' of your sound card's SPDIF output that
> is somewhat unnerving. SPDIF Out from a PC should primarily be an
[quoted text clipped - 4 lines]
> but bottom line, from my understanding, is it's either sending data or it's
> not.

Well, it's conceivable that the volume could be controlled, if there are
control signals being transmitted along with the data. But, as I said in my
original post, I know nothing about this particular protocol, so I guess I
was trying to find out if this is indeed the case. Cyrus mentioned that his
PC can control the SPDIF output level, so I may just have to experiment.
However, I don't have anything with an SPDIF input, so I'm not sure how I
can experiment.

> And I would say it's safe to assume that anything receiving the signal from
> a PC's SPDIF Out would HAVE to be amplified, thus my concern with the fact
> you CAN control its volume.

Level control and amplification are two different things though.

> I would also worry if your PC Sound card has
> some sort of garbage amplification on this line as well, which I wouldn't
> want either. What Sound Card is it?

What's worse...it's a built-in sound card on the motherboard (using the VIA
AC97). It's an ITX motherboard, so it only has one PCI slot and built-in
everything. The PCI slot is currently being used by an external USB card.
If I felt the sound card warranted being changed, I'd probably replace the
USB card with another sound card, disable the on-board sound, and buy a USB
hub to do what the USB card is currently doing. But I have no evidence as
of yet that it's worth doing. And if I can get the SPDIF to work, then
there will be no reason to do it.

> I'm interested to know now for my own understanding. If it's 'integrated
> sound' - ie - built-in to the motherboard odds are very strong it's not a
[quoted text clipped - 5 lines]
> Now, don't take MY word for gospel - this is just what my understanding is
> but I can't posture myself to really *know*.

You may be interested in Arny Krueger's site, where he's tested a number of
sound cards. Mine's apparently not there.

http://www.pcavtech.com/soundcards/compare/index.htm

He shows up in here from time to time.

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Matt Bhame - 08 Apr 2004 20:38 GMT

Cool, thanks man.

> You may be interested in Arny Krueger's site, where he's tested a
> number of sound cards. Mine's apparently not there.
>
> http://www.pcavtech.com/soundcards/compare/index.htm
>
> He shows up in here from time to time.

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cyrus - 08 Apr 2004 09:04 GMT

If your software volume works for your spdif out, i seem to remember
seeing "flying cow" d/a converters with a 120v->12v wallwart at about
500ma or abouts.

Still not sure what bovine in the air have to do with audio.

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cyrus

*coughcasaucedoprodigynetcough*

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cyrus - 08 Apr 2004 09:09 GMT

In article
<invalid-C7BF00.01154608042004@newsclstr01.news.prodigy.com>,

> > So I was thinking of getting a line driver to interface between my computer
> > and amplifiers, because the sound card output is rather low and, on my sub
[quoted text clipped - 9 lines]
>
> Still not sure what bovine in the air have to do with audio.

120vac->12vdc that is.

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cyrus

*coughcasaucedoprodigynetcough*

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