Audio - EQ

See KB/Linux/Desktop/Audio/pipewire.txt for packages
See KB/Linux/Desktop/Audio/pulseaudio.txt for packages

This document outlines how to get a decent audio setup utilizing a headphone EQ called dsp. It's targeted for Linux machines, but use EqualizerAPO to similarly use headphones EQ presets.

See HiFi 24bit and 192kHz Music Downloads are Very Silly Indeed why not more than 44.1 kHz is needed. The following will not enforce 44.1kHz though.

Why?

A target curve T has been tested and be found most comfortable listening to. Try to get each Headphones with EQ settings near that curve T. EQ presets for a lot of headphones.

How-to for Linux

Baseline for this is the following website.

With PipeWire

Use PulseEffects presets for EQ settings and enable auto-start of PulseEffects.

There are some very convenient settings you probably want to set.

Handle suspend
- In /etc/pipewire/media-session.d/media-session.{conf|confpause} comment out suspend-node to enable suspending feature
- In /etc/pipewire/media-session.d/alsa-monitor.conf set a timeout so that your DAC/output device is able to always receive a signal if you like.
```
node.pause-on-idle      = false
session.suspend-timeout-seconds = 0 # or any number as seconds
```
If you like, set a default sample rate in /etc/pipewire/pipewire.conf, e.g. for 44.1kHz
```
default.clock.rate        = 44100
```
Use systemctl --user restart pipewire-media-session.service pipewire.service pipewire-pulse.service to restart PipeWire

With PulseAudio

Allow direct communication to device for PulseAudio. Edit ALSA configuration /etc/asound.conf.
```
# Use PulseAudio plugin hw
pcm.!default {
    type plug
    slave.pcm hw
}
```

(OPTIONAL, DO IF YOU WANT A REMAPPED VERSION OF MAIN AUDIO DEVICE IN sink_name=) Add some default sink names (remap them) in PulseAudio /etc/pulse/default.pa. Use pacmd list-sinks and pacmd list-sources to list your devices and insert as master below. Any user could use sink_main and src_microphone instead of the specific device as sink_name=. This is OPTIONAL if you use direct sink name in any user specific file later instead of "sink_main" and "src_microphone"

# create remapped sink/sources with proper names and description
# pacmd list-sinks
load-module module-remap-sink     sink_name="sink_main"      master="alsa_output.pci-0000_31_00.4.iec958-stereo"              sink_properties=device.description="Toslink"    remix=no
# pacmd list-sources
load-module module-remap-source source_name="src_microphone" master="alsa_input.usb-Samson_Technologies_Samson_Meteor_Mic-00.analog-stereo" source_properties=device.description="Microphone" remix=no

Adapt .config/pulse/daemon.conf

flat-volumes = no

default-sample-channels = 2
default-channel-map = front-left,front-right
default-sample-format = s32ne
;default-sample-rate = 44100
;alternate-sample-rate = 44100
;resample-method = speex-float-10

enable-lfe-remixing = no

high-priority = yes
nice-level = -11
realtime-scheduling = yes
realtime-priority = 9
rlimit-rtprio = 9

EQ

Install dsp.

Create and adapt configuration for dsp. See example below. Use EQ presets for your headphones.

Basic file structure

.config/ladspa_dsp
├── config_beyerdynamic_dt1990
└── eq
    └── beyerdynamic_dt1990.conf

The main configuration for an additional Pulse sink .config/ladspa_dsp/config_beyerdynamic_dt1990
```
LC_NUMERIC=C
effects_chain=@eq/beyerdynamic_dt1990.conf
```

The EQ settings derived from the target curve found for your headphones, e.g. .config/ladspa_dsp/eq/beyerdynamic_dt1990.conf

# Beyerdynamic DT 1990
# preamp gain
gain -4.0

lowshelf    90      0.7q    +4.0
eq          220     0.7q    -3.4
...

Add a new sink based on above remapped sink_main for the EQ present in .config/pulse/default.pa (also some other reasonable default settings)

# load system defaults
.include /etc/pulse/default.pa

# unload the cork stuff
.nofail
unload-module module-role-cork
.fail

# unload the idle suspend stuff
.nofail
unload-module module-suspend-on-idle
.fail

# dsp EQ stuff for various headphones
.ifexists module-ladspa-sink.so
.nofail
load-module module-ladspa-sink sink_name=dsp_beyerdynamic_dt1990            sink_master="<MAIN SINK NAME> OR <sink_main from OPTIONAL STEP>" plugin=ladspa_dsp label=ladspa_dsp:beyerdynamic_dt1990            sink_properties=device.description="Beyerdynamic\ DT\ 1990\ Pro"
.fail
.endif

Restart PulseAudio, so that the new sink appears. In your settings, select the newly added DSP sink as default one. Maybe restart device.

Linux troubleshooting

Something weird going on? Delete anything except for configuration files in .config/pulse/.
Restarting when changing anything in PulseAudio configuration is highly recommended as some applications might not be able to handle restarting audio system.

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