05-05-2020, 06:20 AM
(05-04-2020, 10:57 AM)shadowlord Wrote: Well it isn’t really a hum (the noise is hard to describe)
And it’s not there when the unit is normally operating.
Just after shutdown the noise starts. It‘s about normal listening volume ( not loud but not faint either)
+1 on the probability of a ground-loop
I'm starting off under the presumption that you are listening to RPI/USB DAC combo through an amplifier and speakers. So:
- Make sure that the 'shutdown' is followed by 'powerdown' (turn the RPI power supply OFF). Is the 'noise' still there?
- If the noise is still there unplug the DAC from the RPi... as the DAC is powered by the RPi the noise should disappear
- No noise... it is very likely that the noise comes from the switch-mode power supply that you are probably using to power up the RPi
- Borrow/buy a 5V regulated power supply (something like this JAMECO or AUDIOPHONICS ) or a 'ground loop' eliminator ( AMAZON or CHOICE )
A silly question but I have to ask it... If the USB DAC is removed (unplugged from the amp) has the noise disappeared (provided that the amp's volume setting is at the same level as before)?
