Eliminating ground loop noise on solar powered minirig+bela sound installation

robinprice

I’m working on an outdoor long term sound installation and have a question.

I have a bela and minirig powered off a solar charger via an UBEC step down buck converter. The buck converter has 2 USB ports that I’m using to power the minirig and bela. When the minirig is running off battery everything sounds great but when it’s plugged in I can hear the bela board thinking, I’m assuming the ground plane is not isolated very well?

Any tips on how to eliminate this high pitched electrical noise and whine that I pick up every time I run a patch?

giuliomoro

hi, is this a full-sized Bela or a BelaMini?

robinprice

full size Bela

giuliomoro

We'd normally recommend using two different power supplies, but I see how that would be complicated in this case. Could you try plugging the minirig's USB cable into the BeagleBone's USB port? That may improve things a bit.

Another alternative to experiment with is to power the minirig from P9.01 (GND) and P9.07 (GND). Only try this at very low volume and when the minirig's battery is fully charged, because the current available through P9.07 is limited to less than 500mA. If this gets rid of the hum, the proper way of doing this would be:
- power Bela from the barrel jack
- power the minirig from P9.01(GND) and P9.05 (5V)
when powered from barrel jack, P9.05 will have much higher current capability (it is effectively connected in parallel with the barrel jack input )

robinprice

Ideally I wanted to keep the Bela's USB port free for fitting a wifi dongle so I can still communicate with it when it's in situ. Will try the barrel jack and pin 9.05 / 9.07 route...

Thanks

giuliomoro

when trying that you can also try using different ground pads. Especially P8.01 vs P9.01 could make a difference.