Controlling Volume via Rotary Encoder

Adam Hostetler

June 02, 2025 13:41

None

I'm trying to set up volume control on my amp 4 via a rotary encoder following this guide:

https://gist.github.com/savetheclocktower/9b5f67c20f6c04e65ed88f2e594d43c1

I have the encoder itself talking to the P when I set it to control "Master" (as shown in the "amixer scontrols" results here):

Simple mixer control 'Master',0
Simple mixer control 'Capture',0

However, this does not actually change the volume for the Amp4.

when I run alsamixer, I can see the amp 4 and can control the volume by sliding the 'digital' slider on the far right, but can't figure out how to link the encoder to 'Digital' as that doesn't appear as a valid 'simple control'.

If I set the encoder to control 'Master" and choose that in alsamixer, I can see it moving the slider.

Any ideas on what I need to do to make this work?

Update: one thing I just noticed, my soundcared is lisgted as a dacplus but it's an Amp 4 (not Pro). Is this the issue? if so how do i fix it? I set the dtoverlay to amp4pro (as there's no overlay listed in the instructions for the non pro).

Date Votes

12 comments

0
Adam Hostetler June 03, 2025 20:29
I tried adding
```
pcm.!default { 
type hw card 0
 } 
ctl.!default { 
type hw card 0 
}
```
to etc/asound.conf as detailed here: https://www.hifiberry.com/docs/software/configuring-linux-3-18-x/

but that didn't have any affect.

I then tried adding:
```
pcm.hifiberry {
    type softvol
    slave.pcm "plughw:0"
    control.name "Master"
    control.card 0
```
to etc/asound.conf but that basically crashed the entire audio system and said it was probably outdated when I ran amixer.
Edited by Adam Hostetler June 03, 2025 21:01

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Adam Hostetler June 04, 2025 00:46

ok, I found this article:

https://www.hifiberry.com/docs/software/amixer-multiple-sound-cards-pulseaudio/

which seems to be talking about the problem I'm having but doesn't actually solve it for me as far as I can tell..

Edited by Adam Hostetler June 04, 2025 00:46

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Adam Hostetler June 04, 2025 00:55

Here's the section of code that references the soundcard (anywhere that references 'Master') .. Is there a way I can adjust this to force it to reference the hifiberry? Maybe somehow modifying the amixer lines with the -c 0 command from the above article?

 self.volume = self._constrain(v)
    output = self.amixer("set 'Master' unmute {}%".format(v))
    self._sync(output)
    return self.volume
    
  def toggle(self):
    """
    Toggles muting between on and off.
    """
    if self.is_muted:
      output = self.amixer("set 'Master' unmute")
    else:
      # We're about to mute ourselves, so we should remember the last volume
      # value we had because we'll want to restore it later.
      self.last_volume = self.volume
      output = self.amixer("set 'Master' mute")
  
    self._sync(output)
    if not self.is_muted:
      # If we just unmuted ourselves, we should restore whatever volume we
      # had previously.
      self.set_volume(self.last_volume)
    return self.is_muted
  
  def status(self):
    if self.is_muted:
      return "{}% (muted)".format(self.volume)
    return "{}%".format(self.volume)
  
  # Read the output of `amixer` to get the system volume and mute state.
  #
  # This is designed not to do much work because it'll get called with every
  # click of the knob in either direction, which is why we're doing simple
  # string scanning and not regular expressions.
  def _sync(self, output=None):
    if output is None:
      output = self.amixer("get 'Master'")

0

Adam Hostetler June 05, 2025 00:37

can someone from HiFi Berrry at least tell me if this a lost cause and I should stop trying? The silence is deafening. Should I be tryign this method instead?

https://github.com/hifiberry/audiocontrol2/blob/master/doc/rotary-controller-plugin.md

IS that option exclusive to HifiBerry OS?

Edited by Adam Hostetler June 05, 2025 00:51

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HiFiBerry team June 05, 2025 04:51

As you're refering to some 3rd party software that none of us knows, there is nothing we can say about this at all. You should contact the author of the software.

The Audiocontrol plugin is part of HiFiBerryOS. While you can use AudioControl without HiFiBerryOS, it's not "plug-and-play". You need to understand teh architecture, configuration and setup.

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Adam Hostetler June 05, 2025 09:51

Thanks for getting back to me. I'll look into switching to Hifiberry OS.

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Adam Hostetler June 05, 2025 14:27

Also, in reality all I really need to know is if there's a way to make the amp4 appear as an available 'simple mixer control'. Amixer isn't third party software is it?

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HiFiBerry team June 05, 2025 15:22

I'm not sure what you mean exactly. Your first picture shows that the "Digital" mixer control is available. What do you mean by "make it available as a simple mixer control"?

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Adam Hostetler June 05, 2025 16:30

when I run 'amixer scontrols' "digital' doens't appear as an option. Only 'master' shows there. I can control 'Master' but THAT doesn't actually change the audio coming out of the Amp4.

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Adam Hostetler June 05, 2025 17:01

are 'amixer' and 'alsamixer' two unique programs? Why can alsamixer see it but amixer can't?

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HiFiBerry team June 06, 2025 05:10

You probably have Pulseaudio or Tripwire running and the ALSA subsystem is using this as the default sound card. In this case, you have to specify the sound card explicitely when running amixer:
https://www.hifiberry.com/docs/software/amixer-multiple-sound-cards-pulseaudio/

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Adam Hostetler June 07, 2025 20:50

SO this is freaking nuts... Chatgpt filgured it out for me... I had to disable Pipewire, as it was blocking the controls for the Amp4 somehow. Here's how I did it:

Run the following to disable PipeWire for your user:

systemctl --user stop pipewire pipewire-pulse
systemctl --user disable pipewire pipewire-pulse



1. Stop PipeWire (User Services)

Run these commands:

systemctl --user stop pipewire pipewire-pulse



2. Disable PipeWire at Boot (User Services)

systemctl --user disable pipewire pipewire-pulse



3. Mask It (Prevents It from Being Started Manually or by Dependencies)

systemctl --user mask pipewire pipewire-pulse

❗ Tip: If you get errors like "Failed to connect to bus," run this first: (I did not have to do this)



export XDG_RUNTIME_DIR=/run/user/$(id -u)

Now this is the result of amixer sonctrols:

Simple mixer control 'DSP Program',0
Simple mixer control 'Analogue',0
Simple mixer control 'Analogue Playback Boost',0
Simple mixer control 'Auto Mute',0
Simple mixer control 'Auto Mute Mono',0
Simple mixer control 'Auto Mute Time Left',0
Simple mixer control 'Auto Mute Time Right',0
Simple mixer control 'Clock Missing Period',0
Simple mixer control 'Deemphasis',0
Simple mixer control 'Digital',0
Simple mixer control 'Max Overclock DAC',0
Simple mixer control 'Max Overclock DSP',0
Simple mixer control 'Max Overclock PLL',0
Simple mixer control 'Volume Ramp Down Emergency Rate',0
Simple mixer control 'Volume Ramp Down Emergency Step',0
Simple mixer control 'Volume Ramp Down Rate',0
Simple mixer control 'Volume Ramp Down Step',0
Simple mixer control 'Volume Ramp Up Rate',0
Simple mixer control 'Volume Ramp Up Step',0


"Digital' is what I need to control the amp4 volume.

Edited by Adam Hostetler June 07, 2025 21:16

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