paronym

I also encountered the electrical noise issue with my new Casio CT-S300 when trying to use the USB port and Audio In simultaneously, and so it was with some interest that I read the conversation between Sam Mullins and JimboKeys about the ground loop. The USB Ground Loop isolator discussed costs £49 here in the UK (actually, there's a newer version called iDefender+), and I was very reluctant to spend that much to solve the problem for a fairly low cost keyboard. But thinking about the problem for a while, I realised that there would probably be a cheaper way to solve it. If the ground loop exists between the USB port and the Audio In port, then surely as long as any of those two ports are isolated, the ground loop should be removed. To test my theory, I purchased a cheap ground loop isolator for a 3.5mm audio jack, and plugged that into the Audio In port. Total cost: slightly less than £5. And it works! The humming/buzzing completely disappears when the 3.5mm ground loop isolator is used. So I'm glad to have been able to solve the problem at 1/10th the cost of going down the route of getting the USB isolator. I just thought I'd share this information in case anyone else is looking to solve the same problem.