- Apr 30, 2016
- Crawfordville, FL
I've been reading and re-reading Blencowe and Aiken on this. Hoping that eventually it'll come to me. Iirc, Aiken doesn't seem to think isolating the input jacks is essential? I may have read that wrong or be partially mis-remembering. Honestly it seems to me there are best practice concepts and then you kind of wing it for your particular circuit and hope for the best.
Ground loops are only going to be a significant problem when there's significant ground return current. The real potential problem with not isolating the jacks (and ultimately the whole circuit ground) from chassis/earth is a shared signal return path and earth ground path. This happens when there is another device that is connected to both the common ground and the earth ground through two different connections, for example, when you run a guitar to two separate amps, the amp chassis are connected together through the instrument cable shield and through the mains electrical ground. The electrons will do what they do. Even though you provided them with a nice signal cable to get from point A to B, they will also inevitably make they're way through the ground wires in the power cables also.