Input noise, Power Supply

jordanwhite

I'm currently using the provided USB - mini USB cable to connect the bela to my laptop, and testing some supercollider effects. Pure supercollider works great. If I send an output signal from my laptop to the bela (using a 3.5mm - 3.5mm cable) then the signal gets noisy.

I assume this is due to a power supply issue, so I'd like to try using my CIOKS DC7 power supply - I'd still be using the miniUSB port of the Bela to connect to the IDE for now, but I guess I'd be using the CIOKS USB B port to connect to the Bela's USB B port. Is this okay and won't break anything? Is it likely to help?

Thanks in advance!
Jordan

giuliomoro

when connecting the board to your computer via two distinct cables you may encounter a ground loop, which is what's giving you issues here. Using a different power supply is unlikely to fix things unless you also remove the USB cable (e.g.: using ethernet may work?).

Normally when the board is "deployed" (e.g.: enclosed in a box, or otherwise running stand-alone) and you don't need to use the USB port to the host, the problem solves itself, but it is indeed annoying during development.

giuliomoro

Solutions to this issue require an isolation transformer on the audio lines