Hi guys. thank you for your answers💖
Now i see that i'm a huge noob!🥲what a shame.🥲
Well. let me explain better. my headphones is a wired one. but the volume is not satisfying specially when i'm out of home. i tried my friend's Bluetooth headphones and the volume was so good with less noise. this made me think if i connect my wired headphones to USB by using some adapters, then maybe i get a better sound, by the way, this custom ROM lacks Sony Hi-Res output support and the only Hi-Res outputs available for my phone in this ROM is Bluetooth and USB DAC in the app. by adding the low volume and clipping bass sounds to this situation (i use EQ with bass frequencies set to high), it makes me think if i can use another method to play music to try my luck. besides, nowhere i can find headphones amplifiers in my country and even if i find one, that would be a low-end one without Hi-Res support and sky-breaking price tag.
No i didn't mean that. however, using the phone's DAC and getting it's output from the micro-USB might be a good idea but now i think that's impossible (i've searched in google about digital and analog signals and learned something this time😅), now i found out the micro-USB connection is digital-only and can't be used to transmit audio signals.
Final Words:
I thought Poweramp's USB DAC output is similar to SW decoder in MX Player app which plays anything unsupported by phone's hardware by using CPU power. sorry, the poverty taught me to try to fool my cheap old gadgets to act like flagships...