Tutorial: Install Alsa-Equal

[The Reverend]

Howdy,

so here is my guide to intsall the alsa-equal plugin to use ladspa based equalizers with the odroid c1+ and odroid hifi shield.

a little note first: I installed the midnight commander first, since its my favourite file manager and it makes things a lot easier but thats optional and involves some not so ok symlinking of libraries.

1: get the alsequal package:

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 wget https://aur.archlinux.org/cgit/aur.git/snapshot/alsaequal.tar.gz

2: create a normal user to create the package:

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 useradd -m -G wheel -s /bin/bash testuser

and add a password for the user

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 passwd testuser

3. we need some more packages installed to make the package

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 pacman -S base-devel
  pacman -S ladspa
  pacman -S swh-plugins
 

4. Now log in as your new user and extract the package you downloaded.
Edit the PKGBUILD and change the arch= to arch=('arm7h')

5. now build the package

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 makepkg

6. time to log in as root again und install the freshly build package:

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 pacman -U pacman -U alsaequal-0.6-13-armv7h.pkg.tar.xz

7. edit the /usr/share/alsa/alsa.conf and add the folowing lines at the end:

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 ctl.equal {
    type equal;
    controls "/home/mpd/.alsaequal.bin";
}


pcm.plugequal {
    type equal;
    slave.pcm "plughw:1,0"; #adjust to match your alsa device you want equalized
}

pcm.!default {
    type plug;
    slave.pcm plugequal;
}



8. edit the /etc/mpd.conf , remove all output devices and add alsaequal as new output devices

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audio_output {
        name            "equal"
        type            "alsa"
        device          "plug:plugequal"
#       auto_resample   "no"
#       auto_format     "no"
        enabled         "yes"
}



IMPORTANT : DONT USE THE WEB INTERFACE TO EDIT YOUR CONFIGURATION, IT DOESNT WORK DONT EVER TOUCH THE MPD PART OF THE WEB INTERFACE

9. reboot

10. since mpd is a seperate user and alsaequal is stored in .alsaequal.bin in the home directory of the user create a directory /home/mpd

11. to adjust alsaequal use

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 sudo -H -u mpd alsamixer -D equal

and maybe you have to chown the .alsaequal.bin in /home/mpd and set the owner to mpd but i am not sure about this.

The part that really sucks is the mpd configuration is broken as hell with the web interface, so if you find that your configuration has been reset for some reason, just edit the mpd.conf manually and restart the mpd by using the /dev/ options in the web interface

[The Reverend]

Howdy,


some time has passed and i spend a long time listening to the odroid dac with and without equalizer. I prefer the alsa equalizer. So today i sat down, fired up baudline the FFT analyzer hooked everything up to my soundcard and took some measurements.

DISCLAIMER: These are no super accurate measurements, i used a cheap onboard chipset of my PC. But an equalization curve was applied to compensate the shortcomings in the HF and LF regions and cables were kept short.

As you can see the odroid dac is going down nearly 5db ... wtf were they thinking? The second picture shows the corrected frequency response using the caps equalizer plugin and alsaequal. All adjustments were made using white noise, frequency sweeps and FFT analysis. Minor adjustments were made later with the DAC back in the chain, since there are some more factors involved in frequency response and sound of the whole system.
Since the overall gain level was reduced a little the DAC doesnt crap out beeing fed -1dB full scale signals anymore, THD also improved by 5-6dB beeing tested with a 1khz sine wave. Further improvements could be made using the mbeq plugin which has more features and frequency bands, unfortunately i hab problems running mbeq and there was sometimes heavy audible distorsion, i will have to investigate that further.

For now i recommend every odroid user to try the equalizer.

[hondagx35]

Hi The Reverend,

As you can see the odroid .....

Sorry but i see nothing.

Frank

[The Reverend]

hmm the attached jpegs dont seem to show, lets try again

here is the uncorrected curve:

DACFresponse2.jpg (175.15 KiB) Viewed 9713 times

here after using alsaequal:

DACFresponse3.jpg (186.04 KiB) Viewed 9713 times

[datto]

Thanks for this tutorial The Reverend,

1. Can you confirm that you had to install the Caps package also ?
2. Would it be possible to share your alsaequal settings for the Odroid Hifi Shield ? (not sure if .alsaequal.bin can be copied around).

I have been contacted by Odroid for a recall of the device following your finding on the HF filter issue.

Regards,
Datto