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PiMusicBox 6 / RPI2b with Dac+ distortion

Junwin

November 30, 2015 22:00

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Hi All, 

Got PiMusicBox running on Pi2b. Bought a HiFiBerry Dac+ to get some quality sound via a Demon amp to some Wharfedale speakers. Been trawling round the forums trying to work out why the sound is distorted and terrible unless PiMusicBox volume turned right down - but then the DAC sound doesn't clip but am less than impressed with the sound. 

I guess I've not got this set up right. I've followed the guides, installed stuff, edited etc/modules, blacklists and settings ini but can't work out what's up. Alsamixer doesn't seem to work so

amixer sset 'PCM'

returns an error.

settings.ini is currently has

output = hifiberry_dacplus

mixer_volume = 50

mixer = software

[alsamixer]
card = 0
control = DSP Program

[stream]
enabled = true

Any help would be much appreciated.

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5 comments

• 0
  
  HiFiBerry team December 01, 2015 05:59

  Hi,

  you need to set the mixer volume to a level where there is no clipping. Clipping can occur at several stages: The DAC itself (if you increase the volume above 0db), but also your amplifier. At full volume, the DAC outputs full 2Vrms, this can be too high for some amplifiers (I wouldn't think this is a problem with your Denon, but I don't know it for sure).
  
  Best regards
  Daniel

• 0
  
  Junwin December 01, 2015 15:01

  So just change mixer_volume = 50 to a lower number? Or is this a different setting? 
  Thanks.

   

• 0
  
  HiFiBerry team December 01, 2015 16:07

  Hi,

  You can try to lower the mixer_volume setting. Unfortunately I don't know PiMusicBox in detail. Therefore I can't say which setting has the be changed to what value. I recommend to contact the author. He might be able to answer this.
  However, the

  card = 0
  control = DSP Program

  is definitely wrong. You can check the output of the command "amixer" to see the mixer controls. As there was some work on the driver done by other developers, these have changed recently. Depending on the kernel version that is used, they might look different. "amixer" will show you the controls that are available on your system.

  Best regards
  Daniel 

• 0
  
  Junwin December 10, 2015 14:46

  Hi again. I took a look at the amixer settings where 'digital' is up at 96%. So I'm presuming that's my problem. Only thing is in changing this, on reboot it returns to 96%. Do you know if there's a way of making this stick?

  I noticed others on PiMusicBox forums using a host of different stuff for 'control'. control = digital, control = pcm, for example. I'm not too worried about using PiMusicBox software volume control, just get the output to the Denon right and use the amplifier's own volume control.

  Card 0 is the HiFiBerry Dac+ so I'm presuming that setting is ok. In your experience, setting the mixer as 'alsamixer', card = 0 and control = digital should let me use the Alsamixer digital setting to control output volume? 

  Thanks in advance.

• 0
  
  Junwin December 15, 2015 23:27

  OK - to any trying to anything similar to me, the settings in my original post are fine. I got them here -  Bram_Maes https://discuss.mopidy.com/t/attached-new-hifiberry-dac-but-now-musicbox-local-stopped-working/519/7 - which work. control = DSP Program seems to allow use of the Musicbox.local url for music playing web interface.

  The Amixer output was way high creating distortion. For users of PiMusicBox, file /opt/musicbox/setsound.sh resets your amixer volume each reboot. On Github https://github.com/pimusicbox/pimusicbox/pull/309/files, I've set the  line 128 to VOLUME=70 and this is producing sound with no distortion.

  Now it's working, I can't say I'm overwhelmed with the DAC sound, though.