Help me understand Android Audio

So I hear a significant difference in the audio output with my new Mate 20 Pro vs my old LG G4. Using the same MP3's which I transferred from my computer and listening in my car, the sound is hard to describe. There's definitely some distortion in the treble (cymbals) with lack of "punch" (snare drum). Compression maybe?

There's probably nothing I can do about it, but it got me wondering about the hardware between phones. How different can they be when I'm not using the built-in speaker or headphones? Thanks

The phones can have different audio hardware, especially the DAC's for using the AUX/headphone port. Some are obviously better than others, and LG is known for having some of the better chips for that (especially in the V-series of phones).

Since you're hearing distortion in the Mate 20, I'm also going to guess it has a lower powered amp as well, which is struggling to play at full volume. You can test this by reducing the volume on your phone (to 75% or less) and increasing the volume on the stereo. If it sounds better that way, then there's your issue.

Depends, what are you using to connect to your car? AUX? BT? This has actually nothing to do with Android because this is universal for all music playing devices sending audio to a speaker/headset. Whether it's an iPhone, a Zune, an iPod, Windows Phone, Android device, Windows laptop or whatever else you can think of. If you're connecting an AUX, then the phone decides the quality based on what hardware it has.

If AUX, the quality is decided by the phone HARDWARE, Mooncatt stated above. Mp3 file goes to the phone's built in DAC, which then converts it into analog format which the 3.5mm jack transmits.

Now the Mate 20 DOES NOT have a 3.5mm jack. I'd assume you're connecting it to a USB port on your car's system. If so, then it is the Car's own DAC in it's sound system that's being used, for better or worse. Same would apply if you're using the USB connection on your LG.

If you're using BT connection, then it would depend on the bitrate of the codec you're using to transmit. The LG G4 is pretty old. Not sure if it's capable of using AptX, but in all likelihood it's still using SBC codec to transmit, which maxes 320kbps. Newer phones like the Mate 20 are able to transmit the audio through BT using AptX HD (576kpbs) or LDAC(990kbps). Then you also have to consider your speaker system in your car. How new is the hardware? Is the receiver capable of receiving AptX HD (LDAC is so far Sony proprietary, so only Sony speakers/headsets have it).

If the car system is capable of receiving AptX HD, but the LG is only sending it in SBC quality, then that's what it will play. But if the Mate 20 sends it at AptX HD, then the speakers will play AptX HD.