Hum/noise when not playing

zoom

Hi,
I have hifiberry DAC+ Pro with Raspberry 3. If it's connected to amp and playback is stopped I can hear hum from speakers. If playing any song even very quiet sections of songs are absolutely clean without any noise, but as I mentioned once playback is stopped hum is there. In other words if on DAC green led is on everything is fine but once led is off noise is there.

Would it be possibly keep DAC turned on all the time even if playback is stopped or paused ? Some config/tweak ?

I tested it as well with USB DAC Fiio E10k and this works fine both when playing same as when not playing.

Thanks
Stepan

hondagx35

Hi Stepan,

did you try to update the kernel?
#41805

Frank

zoom

Hi,
thanks for quick reply, I did update kernel based your guide, currently I'm running:

###### System info ######
Linux version 4.4.38-1-ARCH (builduser@leming) (gcc version 6.2.1 20160830 (GCC) ) #1 SMP Thu Dec 15 18:42:01 MST 2016

behavior is slight different but still not ideal.
- Device booting - slight noise present ( outputs are most probable not connected thus same noise is present as if I have connected cables to the amplifier but nothing connected on the other side. That's fine and I understand why this happening)
- During boot DAC is initialized - green LED on hifiberry DAC turned on outputs are connected and no noise at all from speakers
- Playing song - LED still on and everything is OK
- Playback stopped - once playlist finish or I involve stop/pause manually green light disappear and after around 2 seconds same noise as on very beginning during boot where DAC is not initialized yet.
- Playing again - again everything OK

So that's why I'm asking if there is possibility to keep DAC on for all the time and don't turn it off based on stop/pause button. Because as I mentioned after boot DAC is ON no noise at all and nothing playing....

Stepan

hondagx35

Hi Stepan,

please try to play with the "Auto Mute" settings in alsamixer.

Frank

zoom

good idea,
will try it today after work

and let you know.

thanks
Stepan

zoom

I need to say, it doesn't help me.

still when dac is not in use - stopped/paused after few seconds green light turns off and hum is there. It's same level as when cables to power amp are not conected to any player and act as "antena". btw I'm using dac with dual linear power source to be sure on this. Sure I test it with single power source as well. Both pi+hifiberry and power amp are in class II so there is no way for ground loops via PE wires.
Any idea?
for me would be enought to keep DAC on from boot to shutdown.
Some pareneters must control it...
Thanks
Stepan

hondagx35

Hi Stepan,

Any idea?

Sorry, i am out of ideas.

Have you tried to contact the manufacturer?

Frank