Output from the headphone jack. The battery power is actually downright pathetic. Especially with these cheap knockoff batteries.
MotleyG:
Finding actual power output numbers for phones seems to be an impossible task. All I can go off is what I hear. The HTC 10 has the power to really push decent headphones and have strong bass. It can deliver all the sound I want and more, if I asked for it, but then it'd just be painful.
The LG G8 has some impressive sounding tech (which was a main selling point for me), but it will not handle bumping up anything in the EQ since it just causes clipping and automatically lowering the level to compensate. This is unlistenable as the level keeps going up and down in reaction to the audio output with a slight delay, plus clipping. I've asked about it elsewhere and changed all sorts of settings, but have only been able to reduce the effect slightly. The only way to listen to anything on this phone is to leave the EQ and Tone toggles off. That works OK for my car since it doesn't drive enough bass to start shaking parts of the car that rattle, but with my headphones at work, I might as well be listening to youtube. I also know it's a phone thing since I can hear it with other apps as well.