From alsa-user-owner@alsa.jcu.cz  Sat Dec 19 22:29:29 1998
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Date: Sat, 19 Dec 1998 21:30:22 +0000
From: Shaw Terwilliger <sterwill@dogbert.io.nu>
To: alsa-user@alsa.jcu.cz
Subject: My TB Malibu is _still_ Noisy
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[this is long -- I've tried to be as complete in my description of
 the tests I've done to get rid of this noise]

This shouldn't be happening.  I have a Turtle Beach Malibu card, which
I'm generally happy with.  The only problem is that the right channel
gets noise when run through an amplifier (well, the noise is always
there, it's just noticeable when at medium to high volumes).

I was running the analog output into headphones, or into a stereo
amplifier and getting massive amounts of clicking and popping and
humming (like when moving around windows in X).  

I did move my video cards to the very opposite end of the computer
case, so that the ISA card is 8 inches from the video cards.  This
_did_ help quite a bit, but a seperate layer of noise has appeared.

Last night, as sort of an early Christmas present, I bought a 
Sony STR-DE925 (like Jaroslav has).  I'm quite happy with it...
I'm running sound out of the Malibu through the coax output, through
a high grade digital audio cable, into the Sony.  I'm still getting
noise on the right channel... and it's very much in sync with
the same system events (video) that caused my other problems.

But if the analog signal path is completely bypassed (all channels
except PCM and master volume are muted, so no CD or Line In
or Mic garbage is being mixed), why am I getting this?  Is there
some problem with the CS4237B's DSP?  I can't imagine why this is
happening.

Also, I'm running the Sony STR-DE925 into headphones, so I'm 
not hearing analog signal garbage from my video setup (I can
even turn the monitor off and unplug the VGA cable from the video
card).

There was a thread discussing the "pci_retry" option.  I looked
at my XF86Config and noticed it wasn't enabled.  I enabled it
last night (just to see what would happen).  X seems just the smallest
bit faster, but it could all be an illusion.  However, turning
it on or off has no effect on the noise.  It is off again.

If this makes any difference... I get some noise from the card
even if I'm not in X.  I can just run the rsynth "say" program
(text to speach) and hear a bell-curve rise and drop in faint
hiss about 2 seconds into the output.  This hiss is not related
to the rsynth synthesis as it happens with any combination of
syllables.  However, if I tell rsynth to output at a different
sampling rate (say 22051 Hz instead of the default 8000 Hz),
the rise and fall of hiss happens at a different speed.

A quick test shows:

At 8000 Hz, the hiss/buzz happens in cycles of roughly one
second.  At 4000 Hz, the cycles are twice as long (2 seconds).
My very uneducated guess is that the DSP is accumulating crap
in its channels.  Since it varies linearly with the sampling
rate, it seems digital.  

But... I just did another test:  

Now the cycles have become farther apart, but they still vary
linearly with each other.  It seems that if I move some windows
around between tests, the cycles take a different length.

But this interference happens only in the right channel, and I
first thought it had nothing to do with the video interference.
Now I'm not so sure, since simply moving windows around is
having a direct effect on it.

This sucks.

-- 
Shaw Terwilliger (twig@advancenet.net)

