Mamboberry HD DAC+ v2 - constant noise

[powskii]

Since you have this constant loud noise with either DAC you should be suspicious of *all* your external components. These include

• The downstream audio equipment. One possibility is it's being over-driven by the DAC output.
  
• The power supply. Just because you "have a linear power supply" doesn't mean it's good for this purpose. Try substituting a genuine RPi power supply just to be sure.
  
• The RPi. I have to say I'm dubious but swapping RPis is an easy test.
  
• Grounds (or earths in countries which speak the Queen's English  ). Improper grounding of various pieces of audio equipment can induce hum/noise. Granted this is not as common a problem as it used to be, but it still can happen.
  

Since you've already replaced the HiFiBerry DAC+ Pro this observation might be irrelevant but I've not experienced the issues you had with yours. Since Tim makes it so easy to configure, I've tried both software volume control and hardware volume control with this DAC and it works fine for me with either choice. (I don't believe hardware volume control is a magic elixir, by the way.)

Regards,
Kent

Hi,

Thank you for this precision. By the way thanks for this great work on moOde.

The downstream audio equipment : Dynaudio active speaker 
The power supply / ground problem : maybe yes this would be getting very annoying....

I've just tested with a new Pi 3B+ : same problem on both DAC : constant noise/hum with software volume controller.
Disabled vol controller are OK on Hifiberry and Mamboberry, hardware vol controller is ok on Hifiberry.
So not a Pi problem.
This hum appears only when playing audio from USB , webradios are fine : why is this please ?

Regards,
Xavier