Asus A7V8X and SPDIF input
Lucius Snow
* Here is my configuration *
- Asus A7V8X motherboard
- Realtek AC'97 onboard soundcard (ALC650)
- Windows XP SP1
I have no sound from the SPDIF input (from a 44.1 or 48 kHz - stereo
source). I tried with the CD drivers and also the latest ones from both Asus
and Realtek. SPDIF is checked in the controle volume and i enabled the
real-time monitor. However the SPDIF output works fine.
I already wrote to Asus and Realtek a few months ago but it didn't help. I
also posted on this newsgroup and found many users who had exactly the same
problem. I'm quite sure this is a hardware issue. Realtek adviced me to look
at the revision number of the SPDIF bracket provided with the motherboard.
They mentionned the following revisions "1.01", "1.01t" and "2.01". On my
bracket, i found "2A, 1.00-A01, 02A1637".
I'm quite desperated. It's been since november i'm looking for a solution. I
contacted my reseller but they refused to change the bracket although the
motherboard is still in guarantee. They want me to bring the motherboard and
all the stuff but it has nothing to do with it ! It works perfectly. Plus i
can't remove it from my computer because i need it absolutely to work.
Any help appreciated.
Thank you.
--
Lucius Snow
"I'm not here, this isn't happening" - Thom Yorke
Paul
<mon_merd...@hotmail.com> wrote:
Looking at the ALC650 datasheet, it says:
"S/PDIF Input is implemented on the ALC650 Rev. E or later only, and
this register is for use with that product only."
So, you would have to check the top of the chip, to see what revision
of chip was used on the board. According to the datasheet I have,
the revisions go up to "F". If the ALC650 is a revision between "A"
and "D", it doesn't have S/PDIF input circuitry.
The datasheet for the Realtek ALC650 is inside this file - you
can also find this at the Realtek website:
ftp://152.104.125.40/pc/ac97/alc650/alc650_data.exe
Near the back of the datasheet, there is a circuit for AC
coupling the SPDIF to the ALC650. The Asus adapter bracket
looks like this:
+5V
|
|
R01
C07 |
| | |
RCA -----+-----| |-------------+------ SPDIF_IN
| | | | (to motherboard)
| |
R06 (termination R02 DC level should
| resistor ?) | be 1.65V by
| | calculation.
GND GND
so it looks like the basic form of the circuit is correct.
The issue will be whether the values of R01/R02 are biasing
the ALC650 input to 1.65 volts, which is its input threshold.
Perhaps that is why Realtek is referring to certain brackets -
it could be the bias circuit isn't correct with certain ones.
Also, you cannot use a long cable with this circuit, as
there isn't really enough signal to make this circuit work
well (the circuit relies on the roughly gain_of_10 you get
when linearly biasing a CMOS digital input). Try a very
short cable from your stereo.
That is the best "speculating/guessing" I can do.
This webpage has more information on the various standards.
http://www.epanorama.net/documents/audio/spdif.html
If you do happen to have a good revision of ALC650, another
option would be to get a "SPDIF-all" bracket, as shown on this
page -
http://www.asus.com.tw/mb/mb_accessories.htm
and then, connect via TOSLink optical, rather than
RCA jack. The TOSLink will put out a nice logic signal, and
allow a longer (fiber optic) cable to be used. Assuming
your stereo equipment has optical output as well as coax,
and that you can actually buy the Asus product somewhere.
Good luck,
Paul
Lucius Snow
> Looking at the ALC650 datasheet, it says:
>
> "S/PDIF Input is implemented on the ALC650 Rev. E or later only, and
> this register is for use with that product only."
>
> So, you would have to check the top of the chip, to see what revision
> of chip was used on the board. According to the datasheet I have,
> the revisions go up to "F". If the ALC650 is a revision between "A"
> and "D", it doesn't have S/PDIF input circuitry.
Thanks for this reply, Paul. So i just checked out the chip on the
motherboard, and it's written :
ALC650
237E
So i suppose this is the revision E which means it supports SPDIF input.
> The datasheet for the Realtek ALC650 is inside this file - you
> can also find this at the Realtek website:
>
> ftp://152.104.125.40/pc/ac97/alc650/alc650_data.exe
>
> Near the back of the datasheet, there is a circuit for AC
> coupling the SPDIF to the ALC650. The Asus adapter bracket
> looks like this:
>
> +5V
> |
> |
> R01
> C07 |
> | | |
> RCA -----+-----| |-------------+------ SPDIF_IN
> | | | | (to motherboard)
> | |
> R06 (termination R02 DC level should
> | resistor ?) | be 1.65V by
> | | calculation.
> GND GND
>
> so it looks like the basic form of the circuit is correct.
> The issue will be whether the values of R01/R02 are biasing
> the ALC650 input to 1.65 volts, which is its input threshold.
> Perhaps that is why Realtek is referring to certain brackets -
> it could be the bias circuit isn't correct with certain ones.
Yes, i'm almost sure the problem comes from the bracket. As Asus said
before, there are different versions of it. They just replied me and here is
their answer :
"We're wondering if the SPDIF module has the compatibility problem with your
output device. Since we have another SPDIF in/out module,you can try it to
see if it can match your device... I can arrange the exchang service for you
if you accept this solution. Please let me know the shop you bought the
board then I can contact the local reseller to process this case."
It seems to confirm my thoughts. Of course, i gave my agreement for this
exchange so i'll be able to try with another module.
> Also, you cannot use a long cable with this circuit, as
> there isn't really enough signal to make this circuit work
> well (the circuit relies on the roughly gain_of_10 you get
> when linearly biasing a CMOS digital input). Try a very
> short cable from your stereo.
My cables are around one meter and 75 ohms. I'll try with shorter ones to be
sure though. By the way, i tried also with a DVD player as a source. I
played an audio track (PCM - 48 kHz - Stereo) but the result was the same as
my DAT : no sound. However, my devices are ok because i already made them
work by passing through another SPDIF input on my computer. I used an Edirol
UA-1D device which is an USB / SPDIF interface.
> That is the best "speculating/guessing" I can do.
>
> This webpage has more information on the various standards.
>
> http://www.epanorama.net/documents/audio/spdif.html
>
> If you do happen to have a good revision of ALC650, another
> option would be to get a "SPDIF-all" bracket, as shown on this
> page -
>
> http://www.asus.com.tw/mb/mb_accessories.htm
>
> and then, connect via TOSLink optical, rather than
> RCA jack. The TOSLink will put out a nice logic signal, and
> allow a longer (fiber optic) cable to be used. Assuming
> your stereo equipment has optical output as well as coax,
> and that you can actually buy the Asus product somewhere.
Thanks for the tip, i didn't know i could buy these accessories separately.
If the new module doesn't work, i'll probable use this solution since i've
got TOSLink input / output with my DAT player.
> Good luck,
> Paul
Cheers ;)
the...@hercomputer.com
I'm getting the same problem. I bought the ASUS A7V8X audio version. Game
with the SPDIF and game/usb plate.
I'm getting nothing through spdif. Latest bios, latest drivers. Xp SP1.
ALC650 255E
I contacted Asus and have heard nothing.
The weird thing in the volume control is that the spdif faders are ghosted
out.
If anyone has any tips or knows where I can buy a different spdif plate
please let me know.
Lucius Snow
I haven't got any new SPDIF bracket yet. Asus is supposed to provide me one
for a month !