AUX IN Low Volume issue SOLVED! Rooted Android device required

Hey y'all. Ever since I got my '11 TRD-OR I've been extremely disappointed with the super low volume I've experienced with the AUX input. My previous vehicles had tape decks that I could use an adapter in, and I owe way too much on my truck still to buy a replacement head unit!

My solution to this involves using my Android phone with Superuser privileges to modify the libraries where the device learns how loud to make the headphone jack.

I can't (...or won't?...) help you root your phone. And iPhone users, you're iScrewed. But if you are in my predicament and also delve into the world of Android hacking and modifications or have been toying with the idea, we'll get you fixed right up!


Using a root file browser, navigate to the folder /system/etc. In this folder you will find a file called "mixer_paths.xml". Make a copy of this file and save it somewhere in case you accidentally screw something up!

Open the original XML file with a document editor that has Superuser access. Every phone's file will be different, but for myself (Moto X Pure Edition 2015) and a friend (Samsung Galaxy S5) the code we needed was near the bottom of the file. There will be several <path> tags for speaker volume, microphone levels, headphone, line out, and some other miscellaneous audio hardware depending on your device and what it is equipped with. Find the <path> classes for BOTH "line" and "headphones".

There will be a few parameters in each <path> class. If your device supports stereo (what doesn't these days, right?), there will be TWO volume levels in EACH class. I don't know what yours is set to or what you should set it to. Simply use the cursor and the keyboard to change the values, and be sure to save the file when you finish. A reboot is necessary to observe any change.

Use your head, don't go doubling or tripling the volume parameter values. You could vert easily damage the phone or your car stereo. Mine was pre-set at 128. I bumped it to 240 which wasn't enough. Bumped again to 275 and it was way too much. Sitting pretty at 160 right now. This will vary for every different phone, so be patient and make sure you get it right. You don't want the speakers clipping, but I KNOW you want them to be significantly louder.

Below is a pastedump of MY mixer_paths.xml file highlighting the values I edited. Again, yours will look different, there are hundreds and hundreds of lines of code in that file, and I found these down near the end. The only lines I edited in each <path> class were:
<ctl name="HPOUT1 Digital Volume" id="0" value="160" />
<ctl name="HPOUT1 Digital Volume" id="1" value="160" />

These values were 128 originally. Yours may be any number, the number is arbitrary. Volume IDs 0 and 1 correspond to Left and Right, respectively. I wouldn't recommend going more than 20-25% higher than its current value, but you're an adult and can make your own decisions. Here's what the code looked like where I found it, with the headphone and line <path> classes. They were right next to each other, in order.

Code:

<path name="headphones">        
<ctl name="SLIM_0_RX Channels" value="Two" />        
<ctl name="HPOUT1L Input 1" value="SLIMRX1" />        
<ctl name="HPOUT1R Input 1" value="SLIMRX2" />        
<ctl name="HPOUT1 Digital Volume" id="0" value="160" />        
<ctl name="HPOUT1 Digital Volume" id="1" value="160" />        
<ctl name="HPOUT1 Digital Switch" id="0" value="1" />        
<ctl name="HPOUT1 Digital Switch" id="1" value="1" />    
</path>    

<path name="line">        
<path name="headphones" />        
<ctl name="HPOUT1 Digital Volume" id="0" value="160" />        
<ctl name="HPOUT1 Digital Volume" id="1" value="160" />        
</path>

Those four little numbers were all that was standing in my way of having listenable music in my pure stock Tacoma. Hopefully someone else will find this useful.


A DISCLAIMER: be careful with headphones after making this alteration. Increasing the volume parameter by 20-25% could blow out the headphones or damage your hearing if you plug them in at full blast.