Does it exhibit the problem with no input connected? Have you tried it with another source? Could be an issue with your preamp.
Nuforce STA200 issue. Rumble every couple minutes
I just picked up a used NuForce STA200.
I have it connected to a low gain tube amp, ~6db
If I let it sit there with no music (same with music) it will cause a major 'rumble' and the speaker driver is pulsating like crazy for a couple seconds.
This happens every couple minutes.
Any ideas?