spdif static?

Archived from groups: rec.audio.tech (More info?)

I've got a Zapco dac (for the car). I hooked it up to the spdif output on a
sound card and I get max-volume white noise-like sound on top of the music.
This noise completely overwhelms the music.

What I've gotten from Zapco (so far) is that the sound card is the "wrong
frequency". Can anyone explain what they may mean by this? And, more
importantly, does anyone know of an easy way to fix it? The unit also has a
toslink input that I could use if that's easier. To make matters more
complicated, I don't have an available PCI or ISA slot, but I do have USB.

PS - relevant info from the Zapco manual: "Digital Input: AES/EBU, IEC 958,
S/PDIF, EIAJ CP-340" and "44.1 or 48kHz"

--
Mark
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Archived from groups: rec.audio.tech (More info?)

Another update: switching off the de-jitter circuit gets it to work. So
nevermind.

But it does bring up another question...

How "good" is the signal? When playing a wav through winamp, is the
resultant digital output "perfect"? Or can there exist noticable
deficiencies due to the software or anything else really? Note that I'm not
talking about a/d conversion on a line-in, but strictly output.

--
Mark
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"MZ" <zarellam@twcnyremove.rr.comspam> wrote in message
news:rY-dnfedpcSpTT_dRVn-hw@giganews.com...
> PPS - here's a piece of very relevant info from the manual (by the way,
the
> manual is available in pdf on the zapco.com website - there's only one DAC
> there):
>
> There are apparently some switches inside the unit. One of them is a
> "de-jitter enable/disable switch". The manual states: "You would never
want
> to disable this circuit unless 1) your CD transport is out of spec and its
> clock rate is off more than 200 parts/million; 2) you wish to listen to
> 48kHz audio from DDS satellite or DAT and do not have the correct
crystal."
>
> --
> Mark
> remove "remove" and "spam" to reply
>
>
> "MZ" <zarellam@twcnyremove.rr.comspam> wrote in message
> news:zuCdnW9e5r1lUz_dRVn-sA@giganews.com...
> > I've got a Zapco dac (for the car). I hooked it up to the spdif output
on
> a
> > sound card and I get max-volume white noise-like sound on top of the
> music.
> > This noise completely overwhelms the music.
> >
> > What I've gotten from Zapco (so far) is that the sound card is the
"wrong
> > frequency". Can anyone explain what they may mean by this? And, more
> > importantly, does anyone know of an easy way to fix it? The unit also
has
> a
> > toslink input that I could use if that's easier. To make matters more
> > complicated, I don't have an available PCI or ISA slot, but I do have
USB.
> >
> > PS - relevant info from the Zapco manual: "Digital Input: AES/EBU, IEC
> 958,
> > S/PDIF, EIAJ CP-340" and "44.1 or 48kHz"
> >
> > --
> > Mark
> > remove "remove" and "spam" to reply
> >
> >
> >
>
>

Archived from groups: rec.audio.tech (More info?)

> > I've got a Zapco dac (for the car). I hooked it up to the spdif
> > output on a sound card and I get max-volume white noise-like sound on
> > top of the music. This noise completely overwhelms the music.
>
> What happens if you hook it up to some other digital source?
>
> > What I've gotten from Zapco (so far) is that the sound card is the
> > "wrong frequency". Can anyone explain what they may mean by this?
>
> They really don't know. Getting pure noise out of a DAC happens, but
getting
> noise and music mixed together is a new one on me.
>
> > And, more importantly, does anyone know of an easy way to fix it?
>
> It's either the source, the DAC or the context. Mix and match other pieces
> until you narrow it down.

Unfortunately, I don't have another source handy. But I did use the spdif
out of this sound card to successfully drive a set of Boston computer
speakers. Anyway, turns out that disabling the "de-jitter" circuit fixed
the problem. However, the sound quality is not very good. I haven't yet
isolated what's at fault. I'll first verify that the problem isn't post-DAC
by hooking up aseparate analog source to the amplifiers (this worked fine
before). Next, I have access to an audigy2 usb piece with optical that I
can use to see if it's the AC97 onboard sound that's the culprit. I don't
suspect it would be, though, because there's supposedly no variability
between sound cards in terms of a pure digital output. I guess the
exception to this would be if there is some sort of processing going on
(like 3d effects and so forth), but I haven't found this option in the
mixer. The other possibility is that the computer software is somehow at
fault, but I don't know how.


>
> > The unit also has a toslink input that I could use if that's easier.
>
> It would be interesting to know how the DAC works from that input. Given a
> choice, I'd always pick optical in a car.

I'm only running about 12 inches from the computer to the DAC.

Archived from groups: rec.audio.tech (More info?)

> > I don't suspect it would be,
> > though, because there's supposedly no variability between sound cards
> > in terms of a pure digital output.
>
> I disagree with that idea.

I suppose that my lack of understanding is based on not knowing the amount
of processing that the sound card is responsible for to produce the spdif
output. How much variability is there? Especially with an AC97 codec
which, to my knowledge, is usually shunned.


> > I guess the exception to this
> > would be if there is some sort of processing going on (like 3d
> > effects and so forth), but I haven't found this option in the mixer.
> > The other possibility is that the computer software is somehow at
> > fault, but I don't know how.
>
> It's probable that your sound card's output is running at 48 KHz, and the
> DAC doesn't like this.

Yes, I believe it is running at 48kHz. There's nothing in the options or
jumper settings that will allow me to switch it to 44.1kHz. Is the audigy
piece I mentioned 44.1kHz capable? Also, is there any degradation by using
USB 2.0 as the interface for audio?

>
> >>> The unit also has a toslink input that I could use if that's easier.
> >>
> >> It would be interesting to know how the DAC works from that input.
> >> Given a choice, I'd always pick optical in a car.
> >
> > I'm only running about 12 inches from the computer to the DAC.
>
> Really, distance doesn't necessarily matter. There could be grounding
> problems, some hidden.

I considered that. The amplifiers are all grounded correctly (no ground
loops with an analog source), the DAC is grounded to the same distro block,
but the computer grounding is a bit tricky. Running the analog output of
the computer sound card directly into the amplifiers gives me what sounds
like a ground loop whine (but not "alternator whine" ). But I would think
that noise along the digital line would give me dropouts or something. This
hasn't been the case.

Archived from groups: rec.audio.tech (More info?)

> >Is the audigy piece I mentioned 44.1kHz capable?
>
> Nope.

The same kind of protocol differences exist with the optical connection as
well? I thought there was just one standard for toslink?

So how do I get a 44.1kHz USB sound device? Do you know of any?

Archived from groups: rec.audio.tech (More info?)

> > So how do I get a 44.1kHz USB sound device? Do you know of any?
>
> Good question. The first couple of things I tested were 48 KHz. I think
> that USB is the evil word. Some of M-Audio's USB product might be 44.1
KHz,
> but its not exactly cheap.

USB is my only option because the one PCI slot that I have is currently in
use by a USB card (I'm forced to use the USB card in addition to the
on-board USB ports because the computer will not wake with those ports when
I turn on the touchscreen, regardless of what the BIOS settings say - but it
will wake with the PCI card).

The alternative that Zapco offered was for me to send them the unit and
they'd replace the crystal with one for 48kHz. That is, assuming this is
indeed the problem and it's not on the computer side.

I guess I'll make that determination this weekend by performing two tests:

1) Using the RMAA software on the analog output of the sound car to see if
it looks as ridiculous as it sounds (the analog output of the sound card
also sounds bad going directly into the amplifiers). If the frequency
response attributes look similar between the analog output of the sound card
and the analog output of the DAC (being driven by the digital output of the
sound card), then it may provide a clue that the computer side of things is
at fault.
2) Using the audigy USB piece to see if there's any difference.

Thanks for all your help. Any other suggestions?

Archived from groups: rec.audio.tech (More info?)

Today I disabled the on-board sound and used a USB Sound Blaster "MP3 Sound
System" with the optical output. Problem solved.

Would I be better off with another device? Is this device transparent
enough?


--
Mark
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"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:1K6dnUsE_PjzWz7dRVn-vA@comcast.com...
> MZ wrote:
> >>> Is the audigy piece I mentioned 44.1kHz capable?
> >>
> >> Nope.
> >
> > The same kind of protocol differences exist with the optical
> > connection as well?
>
> Yes. There may be more optical formats than coax.
>
> > I thought there was just one standard for toslink?
>
> Nope.
>
> > So how do I get a 44.1kHz USB sound device? Do you know of any?
>
> Good question. The first couple of things I tested were 48 KHz. I think
> that USB is the evil word. Some of M-Audio's USB product might be 44.1
KHz,
> but its not exactly cheap.
>
>

Archived from groups: rec.audio.tech (More info?)

> Hmmm. Another Mark Z. Uh-Oh.
>
>
> Mark Z.

Yikes. Even worse is that my middle name begins with a D also...