I recently replaced my interface (that had two headphone jacks and volume pots) with a new interface that only has one of each. My next move was to pull my 13-year-old Rolls HA-43 headphone amp out of the box-o-cables-and-stuff. I noticed that there's a crackling noise audible when you change the volume on any of the sliders.
Here's the weird part: This happens on all of them. (Will double-check that it's all four channels, and not just the first two.) In the same way. And I'm fairly certain that it didn't used to make that noise.
What might have caused this? Is it worthwhile to diagnose and fix, or should I just toss it out and buy a new one?