5.1 sound fluctuates GA970A-ud3 optical out

[jeff1122]

GA970A-UD3
AMD 970/SB950/rev 1.1
AM3+/PCI-E2 0x16/ATX
4 DDR3 4Gig 2-CH/HD Audio/1394
GbE Lan/6 SATA 6Gb/s/4 USB 3.0

I've been using the optical output from the motherboard to an optical amplifier with a 50 ft run to a 5.1 Dolby Digital decoder to a 5.1 amp. After a couple hours the center and front channels will fade. I have tried wired connections from the Motherboard, Xonner Audio card and USB audio. Also Optical out from the three sources. Turned the other sound devices off in the Device Manager. Tried new drivers. The only thing I'm left with is the motherboard itself??? Just playing 1 channel sound there is no problem. Anything I'm missing? And it fluctuates out of the motherboard wired to 5.1 Decoder. And I have replaced the Decoder. Of course with the wired connections there was no need for the optical decoder.

[Vezina]

So is the analog out working properly on the  on-board and on the Xonar or ...?!
Have you tested the digital out of the Xonar ?!
What do you mean by 1 channel sound ,mono ?!

[jeff1122]

Analog out seems to be fine.
Yes the same problem occurs with the digital out on the xonner.
1 channel front right and left, center and subwoofer, rear or satellite right and left.
I was thinking maybe my problem is with windows 7 (64 bit) I just disabled the stereo mix etc. I'll see if the sound levels stay put now.

[Vezina]

If Xonar does the same it s most probable a software problem ,but not at driver level.Or maybe a problem with the hardware you are connecting to the outputs.

[jeff1122]

Thanks, it has not done it since I disabled all the devices under the recording tab (sound settings) still doesn't make sense to me. I'm not using any of those devices.