There's more than one.
48KHz output capability is hardly significant over a 44.1KHz/16bit lossless FLAC, ALAC, etc. It doesn't specify bitrate in the article of course, but if they are going to market 'high definition' audio, that might be 48KHz/24bit. (My guess is the HD downloads to be offered will eventually be 96/24). Even so, that type of lossless audio is going to be hard to discern - especially so with a set of mediocre headphones. The claim that 48KHz will 'vastly' improve audio is nonsense, and you can easily compare some 16bit/44.1KHz and even 24bit/48KHz from the same master and tell me if you can hear the difference. Have someone arrange an ABX test for you. It's difficult, borderline impossible, even for those claiming to have golden ears.
The success of the Pono kickstarter, and the various comments about how awesome music will be after they start selling you 96KHz/24bit tracks at $17.99+ an album is showing the industry that people want it whether or not they can hear it. I have yet to see the advantage over a FLAC pulled from a $3 EBay CD and the 96/24 offerings I've been able to listen to, and I do listen on some decent quality gear.
The only confusion for people there might be the fact that the 96/24 source material through online purchases is typically remastered content - so it should and does sound different than original releases, but not different than say the 44.1/16 CD layer of current Audio Fidelity CDs (remastered in each case - which is the point of these releases).
Headphones (with an onboard DAC) will need to be powered or the onboard DAC will need to pull power from the phone, *definitely* not something I'm interested in since the iPhone 5 rarely gets me through a day if I am using apps or listening to music. Powering an outboard DAC through the lightning cable will just make battery life go down (probably a small amount, but we don't even need that).
Now, an outboard hi end stereo shelf component with a strong DAC connecting to the phone via lightning and receiving digital has potential, as you'd have a strong DAC you can use for various consumer digital inputs (coax, optical, HDMI) and the iPhone would just be another input format. But I understand that the Yamaha Aventage (shelf component) and some smaller devices (HRT iStreamer) already do this. In fact, I'm going to go see what different file formats show up as on a Yamaha streaming digital to their internal DAC as far as bitrate now - I'm curious if it's capped at 44.1KHz/16bit.
Edit: The Yamaha Aventage receivers already allow you to use a outboard DAC with a USB/Lightning cable, but they don't show the bitrate for this option. I'm sure it's at whatever rate you are allowed to put files on the phone. If I remember correctly, you can have 96/24 files in your iTunes but IOS had a lower limit (IOS capped at 48/24 I believe)
[url=https://farm3.staticflickr.com/2903/14155531128_c996e175fb_m.jpg]Image[/url]
Aventage USB Digital In by
danox574, on Flickr
