[LAU] Terratec DMX 6fire 24/96 intermittent static

Hi all, By looking at the archives this seems like it could be the right list since I see a lot of people with a lot of domain experience here. I recently acquired a second hand PCI sound card from the subject and am having some sound quality issues which seem difficult to understand. It is a Envy24/ICE1712 (snd_ice1712) based cards and comes with a 5.25" IO module, although that is probably not relevant. Issue is that when playing something through it, there is intermittent static like distortion in high frequencies. It is not regular, it's character changes but I am unable to correlate it to any externals. * It happens regardless of whether I am sending audio directly via ALSA (directly to hw:0 or not), or with jackd running. * It happens on PCM out 0&1 and 2&3 (haven't tried 4&5 yet) routed directly to HW0&1 etc. * It is not triggered by DAC output level (Analog Volumes page) * Sound coming from line-in, mixed via Digital Mixer is not affected, while simultaneous PCM out mix-in is. * When playing silence issue does not show. * Distortion volume seems to perfectly track sound volume. Whether I play with DAC output levels or actual PCM source level. As far as I understand this chip set, since Line-in through digital mixer is not affected, this rules faults in: * digital mixer * DAC * analog output stage What is left? Something on the driver side? Unreported under/over runs? Something else? Interrupt line is not shared with anything else and nothing unusual gets reported in the kernel logs, or by jackd. Would it help if I recorded the distortion and shared it? Many thanks, Tvrtko