After clean install of 7.8.2 i set up Allo BossDAC with,
Sound card : [allo-boss-dac-pcm512x-audio-eq]
Auto-conversion : [On] Automatic software conversions
...
EQ Enable : [On] | Select to toggle EQ
SOXR Enable : [Off] | Select to toggle SOXR resampling
the /etc/mpd.conf contained,
# Simple ALSA output
audio_output {
type "alsa"
name "DietPi ALSA"
}
Music is playing, Volume slider lets me slide with no effect on Volume.
Enabled SOXR and did a reboot, Volume slider unresponsive as in OP, just dots and cannot be clicked.
Tested with each one below alone only:
mixer_device "eq"
or
mixer_type "hardware"
or
mixer_control "eq"
greyed out as you wrote.
With just,
mixer_type "software"
Volume slider works in o!mpd and increases/reduces Volume.
The /etc/mpd.conf part looks like this now,
# Simple ALSA output
audio_output {
type "alsa"
format "*:32:3"
name "DietPi ALSA"
mixer_type "software"
}
samplerate_converter "soxr very high"
audio_output_format "*:32:3"
In alsamixer i can see Sliders and toggles, increase / decrease / mute volume with Digital slider.
F6 shows,
- default
0 BossDAC
enter device name...
Max Overclock sliders are at 0 and remain there.
cat /boot/config.txt
#disable_camera_led=1
#-------GPU memory splits-------
gpu_mem_256=192
gpu_mem_512=384
gpu_mem_1024=384
#-------Boot splash screen------
disable_splash=1
#-------Onboard sound-----------
dtparam=audio=off
#-------I2C-------------
#dtparam=i2c_arm=off
#dtparam=i2c_arm_baudrate=100000
#-------SPI-------------
#dtparam=spi=off
#-------Serial/UART-----
# NB: "enable_uart=1" will forcefully set "core_freq=250" on WiFi/BT-capable RPi models, unless "force_turbo=1" is set as well.
enable_uart=0
#-------SD card HPD-----
# Comment to enable SD card hot-plug detection, while booting via USB or network.
# NB: This causes contant CPU load and kernel errors when no SD card is inserted.
dtparam=sd_poll_once
#-------Overclock-------
temp_limit=75
initial_turbo=20
#over_voltage=0
#arm_freq=1500
#core_freq=500
#over_voltage_min=0
#arm_freq_min=300
#core_freq_min=250
#sdram_freq_min=400
arm_64bit=1
dtoverlay=disable-wifi
dtoverlay=allo-boss-dac-pcm512x-audio
root@DietPi:~# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: BossDAC [BossDAC], device 0: Boss DAC HiFi [Master] pcm512x-hifi-0 [Boss DAC HiFi [Master] pcm512x-hifi-0]
Subdevices: 0/1
Subdevice #0: subdevice #0
root@DietPi:~# aplay -L
null
Discard all samples (playback) or generate zero samples (capture)
hw:CARD=BossDAC,DEV=0
BossDAC, Boss DAC HiFi [Master] pcm512x-hifi-0
Direct hardware device without any conversions
plughw:CARD=BossDAC,DEV=0
BossDAC, Boss DAC HiFi [Master] pcm512x-hifi-0
Hardware device with all software conversions
sysdefault:CARD=BossDAC
BossDAC, Boss DAC HiFi [Master] pcm512x-hifi-0
Default Audio Device
dmix:CARD=BossDAC,DEV=0
BossDAC, Boss DAC HiFi [Master] pcm512x-hifi-0
Direct sample mixing device
part of dmesg,
[ 2.227705] bcm2835_vc_sm_cma_probe: Videocore shared memory driver
[ 2.227722] [vc_sm_connected_init]: start
[ 2.235715] [vc_sm_connected_init]: installed successfully
[ 2.255106] snd-allo-boss-dac soc:sound: > snd_soc_register_card() failed: -517
[ 2.259523] rpivid-mem feb00000.hevc-decoder: rpivid-hevcmem initialised: Registers at 0xfeb00000 length 0x00010000
[ 2.259844] snd-allo-boss-dac soc:sound: > snd_soc_register_card() failed: -517
[ 2.261877] rpivid-mem feb10000.rpivid-local-intc: rpivid-intcmem initialised: Registers at 0xfeb10000 length 0x00001000
[ 2.262224] snd-allo-boss-dac soc:sound: > snd_soc_register_card() failed: -517
[ 2.267148] rpivid-mem feb20000.h264-decoder: rpivid-h264mem initialised: Registers at 0xfeb20000 length 0x00010000
[ 2.267575] snd-allo-boss-dac soc:sound: > snd_soc_register_card() failed: -517
[ 2.283956] snd-allo-boss-dac soc:sound: > snd_soc_register_card() failed: -517
[ 2.284116] rpivid-mem feb30000.vp9-decoder: rpivid-vp9mem initialised: Registers at 0xfeb30000 length 0x00010000
[ 2.284422] snd-allo-boss-dac soc:sound: > snd_soc_register_card() failed: -517
[ 2.547874] pcm512x 1-004d: supply AVDD not found, using dummy regulator
[ 2.548243] pcm512x 1-004d: supply DVDD not found, using dummy regulator
[ 2.548291] pcm512x 1-004d: supply CPVDD not found, using dummy regulator
Now off for a backup, then i’ll upgrade to beta 7.9.2
: 
. I guess mixer_control “eq” is then not required anymore, also actually it should have been mixer_device “eq” (