[Android Software Development] ephexxis:
phew okay i realize now i totally didn't even address your specific application haha...

so here's how i ultimately control the loudness of the music i play in my car (and believe me i play it LOUD. milpitas in particular is a really small town and at this point i have to believe im known to other frequent drivers because of how often I'm moving all over town).

first, ill set my gates in v4a and also neutron. this is where you'll set your digital preamp gains as well as using the master limiter in v4a if you choose (you should, it's actually more effective at preventing clipping than just dropping gain and in general I'll set it to - 1.9 or -3 dB and forget it because you can then more or less totally safely put your gain wherever is comfortable and be relatively safe, since the limiters job is to attenuate your peaks prior to where they would clip. if you get close to your max headroom, it'll just sound like the loudest bits of your song are being quieted compared to the rest, which sounds like **** and you should make adjustments to your digital gain, meaning lower it, to bring the levels down from the ceiling).

Now, like i said i also use the gain settings in neutron as well. Neutron and a few other players allow you to use something called ReplayGain which is a pretty nifty parameter that is sometimes included as part of your actual music files themselves. your media player can read this value during playback and sets your digital gain to its instructed level. it's used sometimes for normalization across albums so that songs don't seem to vary wildly in volume and destroy your speakers when all of a sudden a loud one comes on.

that being said most music you'll find that's compressed won't have it. however, with Neutron and foobar2k (my player of choice for Windows when i had a desktop) can set a replay gain value to universally apply to all tracks if the tracks don't have their own value. i always set it on neutron to -2.71 dB (some of these values will seem weird but it's cause decibels are in fact logarithmic rather than linear which is why say -4.4dB sounds close to the same distance from -1.9 as -1.9 did from 0) and forget about it, unless I'm testing a new prop or effect that boosts the overall output significantly.

one more additional feature to explain real quick. in Neutron, ill sort of half use its Automatic Gain Control, which you can also find in v4a though they function differently in practice to achieve the same goal, namely to protect your system against overdrive, or excessive peaking. it's sort of a "smart" limiter if you set it up right, with the idea being to reduce gain if your peaks cross a threshold normally up near your max headroom. really i only set it in neutron to get an idea of where i need to have my preamp gain set to have my output peak between 30-80% off the level Guage because it shows a visualization of your output when you're playing music, next to the master gain slider as shown in screens attached. then i can turn it off because i don't actually need it to drop my gain during playback.

from this point, i set my DAC/amp level usually pretty damn high because as you now all know its boosting the signal output by the phone after all the work on the digital side is said and done.

this leaves me free to adjust my phone volume up and down to whatever setting (i like sitting around 90) and most of the time i control everything in real time using my cars volume knob. it's ultimately where you want to be able to max out and not be anywhere dangerous, but this sequence allows me to achieve loudness that i could probably be arrested for.

godspeed