For those who have one of these iPhones, how's the sound quality through the headphone out? Does it still have a lower volume output (like the 5) than the 4 or 4s?

My Wife got a 5C and i compared the headphone out across an iPhone 5, iPod Touch 5th gen and an iPad 4th Gen and i can say that i was very impressed by the 5C output, so much so i've sold all those devices and bought myself a 5C.  I don't know what apple done with the circuit or the DAC but it sounds fantastic and the volume level is enough to drive my Philips L1 and my earphones.  iTunes never sounded so good.  Just my 2 cents.
 
+ Clear sound stage with plenty of detail
+ Muffled sound of iPhone 5 is gone
+ Clean bass, mids and treble
 
- Non so far

Does the new 5 play 24/96 or better files through its internal DAC?

I've no idea about HiRes,  but i am finding the stock 256K iTunes Plus downloads sound great with plenty of dynamics and sound stage on the new 5C.  Head Fiers should go to their local Apple store for an audition.  I have no idea why they don't promote sound upgrade as a feature of the new phones.

That's great. Maybe since this is the closest to a new music device (no new iPod touch) they'll launch this year, Apple improved the 5C's audio.

Can you say that the 5C's volume output is similar if not better than the 4S or 4 (if you tried one)?

I never tried my wifes 4S,  its gone already.  best bet is an audition at apple store.  I think they done a great job on the audio of 5C.  Now if they can fix the glitches in iOS 7 then for me its a phone that does it all.

I sold the iPhone 5 to keep my 4S because of the lower volume. I can't fathom that a newer device has less output power than the older one.
 
Hence may be 5c/5s are back on track in the output power regard.

I hope 5S has sound quality on par with iPhone 4, cause mine is coming next week. For now we know that the chip is new -  Apple 338S1216, I guess Cirrus Logic again.

The 5c should just be a regular 5 with a plastic back, according to all the tech blogs I've read.  Rudi and a few other head-fiers have mentioned better sound on the 5 after installing iOS7.  I didn't really pay attention when I updated, as I already liked the 5 and was mainly focusing on the CCK and external DAC compatibility update with iOS7.

The audio chip in 5C is different from 5 and 5S.

Got a link? I've seen a mention of a different FaceTime camera but didn't see any other specifics.

Jakkal may be referring to the iFixit teardowns:

iPhone 5: Apple 338S1117
http://www.ifixit.com/Teardown/iPhone+5+Teardown/10525/2

iPhone 5C: Apple 338S1116
http://www.ifixit.com/Teardown/iPhone+5c+Teardown/17382/2

iPhone 5S: Apple 338S1216
http://www.ifixit.com/Teardown/iPhone+5s+Teardown/17383/2

^ Yes thanks. If someone find more info about 5S, please share with us.

Thanks. Do we know which Cirrus chips? The tear down give apple branded numbers.
5 - 338S1117
5c - 338S1116
5s - 338S120L

^ Apple has a branding agreement with CS to not label the chips so it'll be a best guess by anybody.

But, here's an update on the 5S from Chipworks:

As we mentioned earlier, we’re seeing a lot of familiar components inside the iPhone 5s. The major standouts being the new A7 processor and two new MEMS devices. We are also seeing a new power management IC by Dialog Semiconductor and a new audio codec and class D amplifier by Cirrus Logic. The Power Management IC by Dialog Semiconductor has the part number 338S1216-A2. The new parts by Cirrus are numbered as 338S1202 for the Class D audio amplifier and 338S1201 for the Audio Codec. Note that the audio codec is ~30% smaller than the codec inside the iPhone 5.

http://www.chipworks.com/en/technical-competitive-analysis/resources/blog/inside-the-iphone-5s/

So,

Audio Codec: 338S1201
Class D Amplifier: 338S1202

I'm guessing an Audio Codec is a more all encompassing audio chip solution that includes a DAC?

Also of note is that the much lauded iPod Touch 5G used the same 338S1117 chip as the much panned iPhone 5, IIRC. I would guess then that the magic sauce was in the amp.

I am kind of curious about the 30% smaller but though. Anyone who wants to take a guess can try Cirrus Logic's low power product section.

[rule]

I actually have a 5S sitting on my desk, never turned on because I'm waiting for a case to come in tomorrow. I would normally be astounded at my willpower but it's been kind of nice not having cellphone reception for one and a half days.

I did hear it at the store for like half an hour and I feel like there may have been a blacker background and less harshness than on my 4S. Take this with a commercial mound of salt because I didn't have one song that was the same as on the store demo model and it was in the middle of Grand Central Terminal.