How does changing the mixer_paths.xml increase volume? I've been trying to boost the maximum volume obtainable through the audio jack of my phone (Nexus 5). Instead of installing equaliser or volume boosting apps, I thought I'd go about this the technical way:

XDA forums suggest a "MOD" that involves modifying your mixer_paths.xml file located at /system/etc/ (root access naturally required) to increase your speaker or headphone volume beyond the set limits:

Find: &lt;path name="speaker"&gt; 
You will see this string just below it: "RX7 Digital Volume" value="88"
The value is the only part we are going to adjust.
For the mod above, I changed the value to "93". 
The default value is "88" and I would suggest not to go over "95".

To change the Headphone volume:
Find: &lt;path name="headphones"&gt; Look for these strings below it:
"HPHL Volume" value="15"
"HPHR Volume" value="15"
Again all we are changing is the values (ensure both are set at the same number).
For the mod above, I changed the values to "20". The default values are "15" and I would suggest not to go over "20".


How does this work? Does Android artificially limit the maximum volume and this "MOD" bypasses those limits? Or does it compromise audio quality?
I visited this some time ago and explored some values within the file. As it can be hard to determine sound quality comparisons, I also compared the visual appearances of waveforms. 

Here's a screenshot of the page:


Link  

Note that I only listen to audio from my Nexus7 though headphones or external speakers.