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Hi,

I have a P4C800-E with onboard SoundMax, here is the wierd thing:

the soundmax can output using normal stereo phones or/and SPID/F for AC3 output.


when I playback a sound file, it plays fine on both outputs, but when I use the light dimmer that controls the level of light in the room where the PC is located, wierd enought... it causes the SPID/F output to start ticking and pausing !

if I take the dimmer to its low range, it is ok, if I take the dimmer to the high range, it's ok, any position in the middle range causes the SPID/F to start ticking.

can anyone explain this ? is there a solution ?


thanks!
 

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Sounds to me like a combination of a bad dimmer and a poor cable. You've probably got both power-line noise and radiated noise.

First, make sure your PC is properly grounded, to a real gound, not an adapter that goes nowhere. Stereos usually aren't grounding, but if yours is, make sure it's got a real ground too.

Next, how "quality" is the S/PDIF cable you're using? They absolutely must be 75-ohm cables, NOT regular audio cables! When using the coax instead of optical, you really do need to use cables with the best shielding you can get. In terms of length, shorter is better, but tests have shown some pretty long cables (40-50 ft. or more) to function ok. If your cable is of good quality, but extra-long, you might need 2 cables with a S/PDIF repeater box (about $50) in the middle. Or you could run optical converters-- with a TOSLINK cable this would cost about $130 U.S..

If your cable is fine, it would be cheapest to try replacing the light dimmer, as it sounds to me like it's really dirty, causing much more electrical noise than most. Get an electrician if you can't do this job yourself.

You don't say where you live, but in the U.S. typically the [celing] room lights are on one 15-amp circuit and the call outlets are on a separate 20-amp circuit. They do meet in the breaker box, but that's usually far enough to suppress this sort of interference. If the cable's OK and a dimmer swap doesn't help, you might need a power line conditioner for your PC and your stereo, talking maybe some serious cash here; I have no specific recommendations for models.

Hope this helps,

-clintfan
 
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