Hoping for wisdom from this crowd. My nightstand headphone setup is an RPi3 with HiFiBerry Dac+ Pro HAT. I’m using DietPi. I’ve tried a couple of different amplifiers and have a persistent hum. The first amp was a CMoy running on a 9V battery. Current setup is a Bravo Audio V2 amp powered by the included adapter. I’ve used the amp connected to my iPhone and had no trouble with humming. Based on that, I’m thinking the ground loop is coming from the RPi3. The RPi3 is powered by an iFi iPower. The RPi and amp are plugged into the same wall outlet. I’ve tried various RCA interconnects between the Pi and the amp and that doesn’t make a difference. Touching the posts on the amp case reduces the hum as does touching parts of the Pi. Any ideas for how to troubleshoot this? Other than the hum, the little system sounds pretty good and looks pretty cool on the nightstand especially after dark.
Are you able try trial one of these risk free? ie return for a refund if it doesn’t solve your issue?
You should have one of the two components grounded and it sounds like both are floating - indeed the 2 prong iPower is not grounded.
This has various adapters that can be used to ground one point in your system, eg the iPower’s DC plug.
There are cheap DIY ways to ground but this is a safer off the shelf possible solution.
Hi Sean - Thanks for your response! I looked at the Groundhog manual and I’m not sure how to connect it to the setup I have. The iPower 5v is connected to the mini USB port on the RPi3. There are no spare RCA jacks on the hifiberry DAC pro. Thoughts?
In the meantime, I tried a Rolls Buzz Off between the DAC and the amp RCA connections. It slightly reduced the buzz but not enough to make the listening enjoyable.
Thanks again for your input.
Kim
I had a hum coming from my pi using the iPower.
Went back to using the raspberry power supply and… no more humming
Hi Kim there is a spade connector with the Groundhog. It clips onto the iPower plug (then the microUSB adapter can be added - push thrm all together). Just push the spade connector onto the plug and you will hear it click into place.
You could also use the USB attachment in any of the Pi USB ports. So you have 2 options.
Hi Steve,
Thanks for your help. Your suggestion completely cleared it up! Using the RPi branded power supply, the buzzing hive of bees is completely gone. I was also able to remove the iPower and the Rolls Buzz Off from the chain. A previous no-name 5v power supply was original issue I guess. I lost track of all the tinkering I did along the way.
In case anyone is interested: the final system is the RPi3, RPi 5v power supply, HiFiBerry DAC+ Pro, and Bravo Audio V2 amp. The RCA interconnects are some short interconnects I repurposed from an iFi Nano iDSD. The headphones are Sennheiser Momentum. It works great and it’s a pretty low cost set up.
Thanks Sean!
If anyone else is having ground loop problems, you can try an isolated sound card.
We have just released what we think is the first Isolated sound card for the Pi. Because it is magnetically isolated from the Pi, embedded noise, hum, ground loops and other noise sources can’t find their way onto the acoustic pathway.
This isolated sound card has super high quality audio output and input. You can use it as a DAC for Roon.
If you are interested, check the Isolated link on our website : http://audioinjector.net/
Matt