From alsa-user-owner@alsa.jcu.cz  Fri Oct 23 22:40:56 1998
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Subject: Re: TB Malibu Noisy Channel
To: alsa-user@jcu.cz
Date: Fri, 23 Oct 1998 15:36:11 -0500 (CDT)
In-Reply-To: <3630BD6E.2E50@erols.com> from "Paul Winkler" at Oct 23, 98 01:31:26 pm
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> One thing to try is muting all the channels, and then un-muting them one
> at a time to see if you can isolate the source of the noise. Do you
> still get the noise if only the PCM and master output channels are
> turned on? I get some noise through the CD-audio cable, and through the
> synthesizer, and a little bit through the line in if I leave an
> unterminated cable attached to it (which I have a habit of doing).

Yeah, it's not any of the input channels.  It's an odd problem... seems
like a DSP problem, perhaps.  If I'm running sound through the PCM
channel, I hear the clicking and popping (very quiet), but in cycles
that match something like a hard drive, video card, etc.  If I 
mute the DSP and PCM channels, nothing changes.  It's still there...
but only when the channel is open for playback.  If I pull the master
volume all the way down (every single channel has a volume of 0, but
not muted) it is STILL there.  If I mute all channels but the master
(and data is still being played), it is still there.  If there is 
data in playback, the only way to make it stop whirring is to mute
the master volume.  

> I don't know if there's an effective way to shield a card inside a
> computer. Moving it to another slot MIGHT help, preferably as far away
> from everything else as possible. But it might not.

I was thinking tinfoil wrapped in paper towels.  :)  Really, I'd try
to move the video card up a few, and shift the sound card down towards
the bottom.  But since it's only on the right channel (not mainly, but
entirely on one channel), and it only happens when PCM data is 
played, and isn't affected by muting the PCM or DSP channels, I'm
really wondering if it's something in the card.

-- 
Shaw Terwilliger (twig@advancenet.net)

