Sound input problems on Shuttle SN68PTG5

Mike Evans mike at tandem.f9.co.uk
Mon Apr 28 21:28:36 UTC 2008


I'm running Fedora 8 on a Shuttle SN68PTG5 - and I've been very happy 
with it so far.

The On-board sound is specified as: 7.1 channel High Definition Audio, 
Realtek ALC888DD codec by the manufacturer.  Soundcard detection shows:

Vendor: nVidia Corporation
Model: MCP67 High Definition Audio
Module: snd-hda-intel

 From what I can tell this implies that there is a Media and 
Communications Processor (MCP) from nVidia, and that is consistent with 
the manufacturer's details: Chipset: NVIDIA GeForce 7050PV and nForce 
630a (Codename: MCP 68PVNT).  I presume that the Realtek chips are 
somehow used for sound under the control of this processor.  Why one 
says MCP67 and one MCP68 I don't understand.

The Soundcard detection only shows options for PCM device related to 
ALC883.  (Analog and Digital.)  Sound output has been working fine with 
ALC883 Analog.

My problem is  when I try to use the sound input - either front mic or 
line-in sockets.  If I start Audacity I see -30dB noise on the left 
channel only, even with no input source connected.  If I feed in a 
signal I see it on the left channel, in addition to the noise, and still 
get nothing at all on the right channel.

Thinking this was a connection or board problem I visited the supplier's 
offices today.  They installed a copy of Vista on it temporarily and it 
worked perfectly.  This led me to believe that the problem must be with 
the drivers.  I was up-to-date with the alsa drivers, lib and utilities 
from the fedora repos at 1.0.15.  On the Realtek site I found a linux 
driver set dated February 20th.  I backed up 
/lib/modules/.../kernel/sound and a few other bits and pieces and 
installed it.  It compiled new versions of alsa-lib and utils but they 
are still 1.0.15.  The drivers however are 1.0.16 and soundcard 
detection shows that it is picking those up.  Unfortunately no improvement.

Any suggestions on how to progress further please.  Yes I know I could 
get a separate sound card, but I'd like to get this one working if I 
can, especially as it works well for output.

Thanks,
Mike Evans




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