All right. I am going to give my review of the iPod touch 5th generation if anyone is interested...
A quick background first. I have been playing piano since I was five, recording and mixing multi track audio since probably 10. I have a very discerning ear. People are always surprised at things I hear that they can't. I had an audiologist exam within the last year, and he was literally impressed that I heard such faint sounds during the test with 100% accuracy. He said it was one of the best he's seen. I don't mean to sound boastful, but I just want you to know where I'm coming from, because audio opinions can very greatly even among audiophiles. Basically, I'm super incredibly ridiculously picky about everything audio.
With that said, the new iPod touch is greatly frustrating me. The audio quality is absolutely not the same as four other iPods I have. I had a classic 160GB which died, but I've compared that to other devices, so I know where that stands. I have a 16GB nano g6, and also a 4GB nano g2. Right now I have the two nanos and my new touch.
For reference, I have an apogee duet interface. I'm familiar with a variety of sound systems. I've had a harman kardon av-r325 with a digital input and now am using a denon avr-990 with infinity alpha speaker system (the larger sizes). I have a Pioneer/JBL audio system in my car and an array of in ear and studio quality headphones. I have alesis m1 mk2 biamp studio monitors as well. The point being that I am always comparing and contrasting different audio systems and very often using the differences of each system to determine mixing decisions with my own recordings.
So, with that background, I've compared the new ipod touch to the older ipods and the duet. The results are frustrating. I don't want to come out and say the quality is worse, however it is definitely different. I don't want to over stress the difference, because to some they may not exist, to others they may be night and day. However, I noticed there was a difference without even comparing devices. I was listening to a recording by the band secret garden, which contains violins and strings, and I thought "something isn't right here". There was a slight lack of clarity, and an almost boominess to certain low/mid frequencies. My first thought was that I actually had an EQ set accidentally (I never use EQ), but after checking there are absolutely no audio settings enabled. The sound is as flat and unaltered as possible on the device. So, I decided to compare it to the nano 2g first, because that was the closest to my classic, which I'm very familiar with. The difference was sort of surprising. The 2g nano is old and still extremely thin and small. The old nano had more clarity. I don't want to call it detail, and I'll explain in a second.
I compared a few different songs of different genres from david benoit jazz to david gates soft rock to secret garden new age, etc. etc. The difference was noticeable in each situation. The more I listen the more difficult it is to determine how this is affecting the 'quality'. I'm thinking the difference might be more of a frequency equalization difference. Further comparing showed that although every device sounds a very slight bit different, they all sound extremely close to the duet (reference) while the new touch was the most far away from the duet in sound. So my first thought is that if all the other devices are similar to the duet, which is a renowned audio interface for it's sound quality, then the touch is the failure here. However, upon intensive listening, I believe the root "quality" is the same or similar, but the frequencies are of a different response curve. You may argue that this is in fact a difference in quality (i would) but not in the same way as what I would consider "sound quality" in the truest sense.
For instance, you can have a smaller stereo separation or less depth to the sound or simply a lack of frequencies (can't be reproduced by the device). As far as I can tell most of these aspects are similar across devices. The differences in songs varied. Sometimes the guitars in a song stood out more on the touch and sometimes drums stood out more clearly on the nano. I believe the reason for this is because the touch has what I'll call a "boost" in the mid/low frequencies and a "reduction" in high frequencies (or possibly the illusion of this because of the added lows). Therefore certain guitars with mid/low range would seem to stand out more on the touch, and crisp drums would on the nano. Both can reveal all of the details of said instruments, and the nuances and atmosphere of the song are similar. The real differences (so far as i can tell) are between the frequency adjustment.
If I had to guess based on experience, I would say the ipod touch 5g has a 1db boost from about 100hz to 350hz and a -.5 to -1db reduction in 15k to 20k both with a smooth rolloff. At least that is what it "sounds" like. It can be very hard to tell if there are other factors in play and the differences may be smaller than that. Sometimes the other devices sound like they exhibit small distortion. I'm referring to the minimal distortion from the amplification system, not clipping from bad recording or mastering... This is almost undetectable, but then listening to the touch seems smoother. This could be a cleaner amplification system, or an illusion from the difference in high eq. The fact that details sound similar makes me think possibly that the audio is cleaner, but it's impossible for me to tell for sure.
I think the main difference is the overal tonality of the eq. I'm on the fence as to whether I should return it or if i may end up liking it. My logical experience part of my brain says it's not good. Everything else is similar to reference, which is the truest the sound should be. Therefore the touch is not being true to the source material. However, being primarily an eq difference, it may not be that bad. There is an enormous eq difference between every pair of headphones and speakers, while this is in the smallest magnitude different from the other devices.
I'm going WAY too long with this, but hopefully it will help someone. I don't want to disuade anyone from getting a new touch. The device is amazing in every single way. Including the audio in such a feature packed device so freaking thin. I may even find that a lot of the difference I hear are exaggerated because I "think" they are. But I have a lot of experience in ruling out placebo type audio differences. I've spent a lot of time training my ears 'and' my brain to detect differences including doing double blind testing on occasion.
I'll end it there for now and update if i find anything new or come to any different conclusion. Keep in mind even though my comparison has been painstaking, relatively speaking it is a new device and i haven't had a 'lot' of time with it. I'd love to hear other opinions of the 5g for those who have one. And i'm glad to answer any specific questions...