Sound Quality Problems ONLY When No Monitor Plugged In
This one has me baffled..
I am using a VIA EPIA CN10000 with a Laptop HD and a Terratec EWX 24/96 sound card. There's nothing else. I'm using Windows XP Pro SP2. I've got everything working fine, digital output and line output from the soundcard are 100% perfect. But, the box is designed to be used without a monitor, keyboard or mouse. When I unplug these and boot up the PC the sound quality is terrible, I get a wierd warbling comingthrough with the sound. It's only when there's sound there, it doesn't happen when the box is quiet. It affects both the digital and analogue outputs from the card but the on-board audio remains fine. I've restored old drive images and can reproduce this easily. I've uninstalled the S3G Unichrome Pro drivers (which have been a bit of a problem for other reasons) but this has had no effect. Plugging the monitor back in doesn't restore the sound quality, only a drive image restore can get it back to sounding okay. This has started to happen since I changed the motherboard from an older, slower VIA EPIA board.
Any ideas? Anything at all would be appreciated, I've now spent 2 full days struggling with this and I've run out of ideas (and patience).