title: Configuring volume control for USB-DAC to be used via mpd
body: <p>I am building a music player system using a Raspberry Pi with Raspbian and a NuForce uDAC-3 USB-DAC.</p>
  
  <p>I got mpd use the DAC instead of Pi's sound system using these lines in /etc/mpd.conf. As far as I know, the essential thing here is selecting hw device 1 instead of default 0.</p>
  
  <pre><code>audio_output {
     type            "alsa"
     name            "My ALSA Device"
     device          "hw:1,0"        # optional
     format          "44100:16:2"    # optional
     mixer_device    "default"       # optional
     mixer_control   "PCM"           # optional
     mixer_index     "0"             # optional
  }
  </code></pre>
  
  <p>The driver used for my DAC (snd_usb_audio) doesn't, however, support hardware volume control. There is no volume control available for it in alsamixer, for example. As far as I know, that's a known "feature" for that driver or it's support for that DAC. I got mpd control the volume by uncommenting this in /etc/mpd.conf:</p>
  
  <pre><code>mixer_type                      "software"
  </code></pre>
  
  <p>The primary problem now is that there is some lag in volume control that wasn't there with the integrated sound system. I mean, when I slide the volume control in my client program (QMPDClient), there is a short but notable delay before the change in volume can be heard. It's bearable but makes me wonder if everything really works as it should.</p>
  
  <p>The second problem, somewhat related to the first one, is that I am wondering if there is a way to make the sound more perfect as far as any configuration files are concerned.</p>
  
  <p>I have tried various examples of /etc/asound.conf I have found on the internet but either I don't understand what they are supposed to do or they simply are not working. What I thought I would get is either a Master volume control for the DAC recognized by mpd or a virtual sound card that would have a Master volume control and that would feed the sound to the DAC. Initially, /etc/asound.conf was empty, and it still is, now that nothing there seems to affect anything.</p>
  
  <p>Just for the case it has any relevance, the music is in .flac files ripped from CDs.</p>