Background noise on AC3 Playback

[KaBeCi]

I've got a CMedia CMI audio card (4ch.) and every time a play a movie with AC3 i get some high frequency background noise all the time (very annoying on low audio scenes). I'm using Valex AC3 Filter 0.68b under Windows XP (same problem under Win98). And i got lastest drivers for my audio card from C-Media site.
This doesn't happen if I play a movie without AC3 (MP3 or PCM)
Does anybody has the same problem??? I search the forum and i found nothing like this...
i got low audible noise on all 4 channels

thanks for answering

[KpeX]

It's hard to say what the source of this noise could be. Take a look here (http://forum.doom9.org/showthread.php?s=&threadid=18318) for more information on AC3. What kind of connection/speakers are you using? Have you tried switching from DirectSound and WaveOut?

[KaBeCi]

I've red the AC3 Q&A and I tryed switching from DirectSound to WaveOut without any success (noise still there)
The problem are not the cables for sure, only AC3 audio plays with noise, and the noise is on the 4 channels, not only on the rear ones. I can play a .mp3 on the 4 channels and no noise.
Today I made some tests... I tryed 2 other audio cards (only stereo) and i could play movies with AC3 without any noise, same PC / Cables /Amp / Speakers, I changed only the audio card, so I really beleive that problem is the combination of AC3, Valex AC3Filter and the Cmedia CMI 8738 audio chip (I got it on a Genius Sound Maker Value 4.1 Audio Card).
I've tryed different players (BSPlayer, RadLight and WMP) and I got the same problem. I also tryed intervideo ac3 decoder, and i can decode AC3 but only to stereo (the same happens to other people with CMI 8738), and with the same f*cking background noise.
This background noise is not a very high frequency, i'd say is a mid-freq one.
Another thing to care is that if I pause or stop the movie, the noise dissappear, and it comes back when i play it.

Thanks for reading and try to help
and sorry about my english (i'm from Argentina)

[Wilbert]

Did you try different drivers?

[KaBeCi]

for my audio card, i tryed the original drivers that came with it and the lastest ones from c-media site.
for ac3 filtering i tryed ac3filter (vartex) and intervideo
i've also tryed Moonlight Odia Dekoda but dont know why, but it doesnt decode ac3, it doesnt register as a ac3 decoder so when i playback a video with ac3 it doesnt load (i've previously uninstalled all others ac3 filters)

[Atamido]

Will it decode the AC3 if you manually connect the filter in GraphEdit?

[markrb]

If it is a PCI card try a different slot as far away from other cards as possible.

It may also be that the card is simply prone to interference and there is little you can do in your setup.

Some cards just won't work right in some systems sadly.

Mark