Are you using the most recent update to the software? There is a poster on xda that is convinced that the DAC works in all apps. He was thinking perhaps it was fixed in the update that came out recently.
http://forum.xda-developers.com/lg-v10/help/audio-quality-t3224271/page2#post63516449
The latest was only UI bugs update last month, if u mean the one just released this week ? No, I actually packed it up and send it back to Korea....that unlocked v10 doesn't have lte in the USA.
Hi-fi icon will be always on, no matter what...I already mentioned it many times before.
http://www.head-fi.org/t/785335/lg-v10-hi-fi-audio-quality-review-on-serious-audio-performance/15#post_12012803
We only had so many pages....follow that link and see.
Any apps others than stock player app can not access the hifi DAC. It gets confusing but I verified it.
***confusing part****
1/ hifi icon will always be on, regardless of apps is running, just as long as you had toggled the hifi on, it remains on with headphones attached
2/ even when hifi icon is on, the volume output does not increase in power output. I was unable to verify it using IM-04 because it was only an in ear monitor.....until I was using MdR Z7, the Z7 did not have enough loudness at 100% and even when toggling on and off that hifi icon.
3/ I switched back to stock app, and when first turning on the player, the volume did not change. But until I toggle hi fi icon off and on again, the Z7 almost blew my ears drums....
I thought it was weird, and tried many times...
***verification and confirming parts***
1/ Then I tried to download neutron player, and power amp. It didn't matter what options did I toggle, within the app, or the hifi icon, non of these app players were able to increase the volume loudness. I knew then the amplification process was out of the Windows.
2/ When opened up neutron player and checked into the hardware, the only codec was arm v6 codec or whatever, and that was the snapdragon DAC. There was no other options to switch to the other DAC.
3/ Then I sat down and used IM04 to listen to my specific song in 96/192. Over...and over....and over again from power amp vs stock player.
A/ yes, toggling hifi on-off will change volume loudness in IM-04 but does not change anything in power amp
B/ the sound quality was obviously suffering, bass was thinner, trebles were more dry, soundstage is much narrower.
Those were my finding. I am sure XDA will fix it, and until they do, let's see how the USA V10 version turn out to be ? Free 200gb memory is a sweet deal
However, if Lg pushed the OTA fix, it would be an excellent fix
let's pray that it does.