Re: [Alsa-user] Terratec DMX XFire 1024 cs46xx module

[Friedrich Ewaldt]

Hi Richard, hi Benny(perhaps you have some idea what's going on ;-))

Richard Stevens wrote:
> [...]
>
> The problem is massively distorted sound. I get the driver loaded and there is
> some sound coming out of the card. But it's distorted. If I set very low
> levels for Master, PCM and DAC in alsamixer the distortion is not that bad
> but I have to set my amplifier to a really high level to even hear something.
> As soon as I set the levels higher distortion gets worse and worse until at
> some stage the right channel disappears and only very distorted sound comes
> out of the left channel. I thought about a broken card but it works perfectly
> with windows.
>
same problem for me and my DMX XFire 1024 :-(.
I think the distortion sounds like a DC offset introduced by the PCM
channel. Do you also get popping noise when changing the PCM volume? It
just sounds like changing the supply voltage of a running amplifier for
me. Perhaps I can measure the DC level before the output capacitors or
--perhaps even better-- at the input stage of the output amps? (But I
don't know if the DAC used on this card can output DC voltage and if the
LM386 amps are AC or DC coupled. I'll have to find a screwdriver and
some time first.)

Not only the PCM sound is distorted, but everything that goes through
the mixer, I think. If you lower the PCM volume and playback e.g. a CD
through the CD input of the card, then the quality is OK.
This seems to be a problem with the XFire only, as none of the other
cs46xx users has reported this problem. Perhaps it has something to do
with the audio codec (the XFire uses one codec for 4 channels, other
cs46xx use two codecs for this)? Or some GPIO?

I have this problem with Mandrake 8.1 and 9.0. The problem also existed
with the old DSP code (before Benny started hacking).
Typing '/etc/init.d/alsa restart' (or 'force-restart' ??? I don't know
exactly right now), solves the distortion problem for me every time.
(But then the rights for the audio devices are gone for users, so I have
to run apps as root or use the ./sndconfig script.) So it must be some
initialization problem. Would it help to compare some /proc/asound/
outputs before/after restarting alsa? If so, which should I look at?

Benny, thanks a lot for your new DSP code. Hardware mixing works great!
I didn't test variable period sizes up to now because I'm using Mandrake
RPMs at the moment. So, patching isn't possible right now, but I'll
change back to tarballs or cvs soon :-). Btw, do you have any idea how
to get 4 indep. channels working with this one codec?

regards,
fritz e.




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