Where you using the SR15 as a BT reciever? Because unless you meant WiFi I don’t know why you’d have Bluetooth enabled if you’re listening to balanced- which of course requires a wired connection. If that’s the case, I’d reccomend and ear studio ES100 which lasts 14 hours and has balanced and sounds great and has Bluetooth 5.0 and LDAC, If I’m understanding you correctly. Or just get a Sony Zx300 or wm 1A and use that, of course you don’t get streaming but you get lots of battery life. Or get the Fiio m6 that has streaming, Bluetooth 5.0 LDAC, sounds great and lasts 13 hours. And use that for flights and active use (as I do). Just sounds like you hate your SR15- but you only get about 6 to 7 hours balanced anyways with such a small dap with a quad core processor. It’s pretty much standard for all the mid tier daps I’ve had except Sony’s and the new Shanling M5s.