I actually don't, like I mentioned I am not a techy tyoe guy and the way the music is recorded on base line levels seems to work really well, I never have wished to adjust them. Like you mentioned it can be done with applications downloaded for a phone. Since the recording is digital and is being played digitally I am told the quality is as good as a CD or actually as perfect as the download. I literally just took out my brothers classic audio head unit and cd player (cost him 1300) from his '65 mustang and installed this simple unit (I machined custom knobs) and used a radio dummy faceplate and he said he should have done it from the begininng. I know you can ask Ryan on this forum, he heard my phone in my '37, clear is clear. I also wired a micro LED to tell when the switch is on (meaning the amp is on and the IS-75)
The other neat thing is if you go to a drive in that plays through the radio, take along a dollar general headphone radio (cost less than 5 bucks or so) and plug the unit into the headphone jack and your good to go. I liked the idea becasue we simply don't know what the future of audio is, but for the past 40 years its been output through a headphone jack somwhere, either radio, cd or mp3
Don't let the price fool you, my buddy just did this in his '62 restomod vette, he left the dummy radio and used a huge amp & speakers and the thing is unbelieveable, extremely loud and very clear, said the same thing should have done it sooner, all through a ipod he uses.