Weird noise from RPi w/ DAC+ Pro

Anirban Banerjee

December 09, 2017 16:23

None

Hi,

I am using the DAC+ Pro with RPi1 B+ and OpenELEC 7.0.1. I have a separate LM7805 LDO for DAC+ and the RPi is powered from the GPIO header pins.

I can hear noise like flutter and rustle when Kodi starts and weird hiss when I scroll the mouse.

This noise goes away completely when I power the RPi via the micro-USB power port.

However, my enclosure does not bring out the micro-USB power port.

Is this a ground bounce issue between digital and analog grounds?

Is this due to powering the RPi via the GPIO header? I have 470uF between the 5V and GND header pins.

Should I get a separate power supply (separate at the AC mains) for the RPi?

Thanks

Anirban

HiFiBerry team December 10, 2017 12:40

designing a system with multiple power supplies is a complex thing to do. There is no easy "fix this" answer to your problem. Without measurement equipment and the knowledge how to use it to debug this, this is something that can create all kind of problems. Most likely there is some kind of ground loop, but I can't tell you why.
We strongly recommend to use a single power supply for the whole system as all HiFiBerry boards already have a linear voltage regulator on board that filters out switching noise very well. Large electrolytic capacitors don't work well for this as they perform quite bad on high-frequency noise.

Best regards,
Daniel

Weird noise from RPi w/ DAC+ Pro

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