Holy cow; I tested a Beyerdynamic A200p DAC and headphone amp at the same time I had the iPhone 6 Plus in my audio lab, and the iPhone 6 Plus beat it! The iPhone 6 Plus has less distortion, flatter frequency response and much better ability to drive low-impedance headphones with low distortion than the dedicated portable amp!
While all iOS devices have always sounded great if you have good transfers, the audio output of the iPhone 6 Plus is now so improved that it sounds and measures about as well as professional reference DACs like the Benchmark DAC1 HDR, and better than manyconsumer DACs.
The iPhone 6 Plus even has flatter response than the Benchmark DAC1 HDR! Of course an iPhone and a plug-in-the-wall professional DAC are intended for entirely different pupposes, but if the 1 volt RMS output (6 dB less than good outboard DACs and CD players) and 3.5mm jack do it for you, there's no reason not to use the iPhone's output for critical listening.
The iPhone 6 is a better analog audio source than many audiophile products, but the cottage industry created around selling you DACs and other accessories you don't need doesn't want you to know. Remember that accessory dealers, manufacturers and publications that accept advertising from these makers have a vested interest in trying to create FUD about the iPhone's audio quality. Don't beleive them and listen for yourself.
Apple has more smart engineers and far more resources than any other audio specialty company. It makes perfect sense that the iPhone output should be spectacular.
No longer do you need to waste money on DACs and headphone amplifiers, at least for most portable (low-impedance) headphones. Save your money and spend it on moremusic instead.
Hint: Always leave the iPhone's level all the way up when using it as a program source fed to preamp.
I was googling for reviews on iBasso and other players and came up with this:
Basically, according to this guy, we should all be using iPhone and through our dedicated DAPs out the window!!!
And then of course theres this bit: