May 04, 2018 · Adjust the equalizer by using alsamixer command. alsamixer -D equal. The sound from Raspberry Pi’s speaker should change as you change the equalizer values. Notes Since Raspbian Stretch, Bluetooth audio is handled by ALSA using bluez-alsa . So if A2DP sink is enabled, this equalizer can be also applied on Bluetooth audio. References def set_alsa_control(self, alsa_control): from alsaaudio import Mixer try: self.mixer = Mixer(alsa_control) logging.debug("using existing ALSA control %s", alsa_control) except: try: logging.debug( "ALSA control %s does not exist, creating it", alsa_control) self.mixer = self.create_mixer(alsa_control) except Exception as e: logging.error( "can't create ALSA mixer control %s (%s)", alsa_control, e) return False if self.mixer == None: logging.error("ALSA mixer %s not found", alsa_control ... Cannot open mixer If you have tried to install a couple of different ALSA versions, then sometimes the mixer cannot be opened anymore. This happens if you have tried 0.3.2 and want to downgrade to 0.3.0-pre4 (IIRC).
See full list on maketecheasier.com alsamixer: function snd_ctl_open failed for default: No such device the right device special files in /dev/ might be missing. Run ls /dev/snd/ and make sure there are several entries there. If the directory does not exist, or it is empty, use the ALSA snddevices script or similar to create it and the device special files in it. What happens if you start a mixer, do you see the card? The channels are muted by default after installation. I have two hunches as to the source of the problem. But first, here's a screenshot of alsamixer. Code: [Select]. Cannot open mixer device 'default'. Connection refused.