the BIGGEST problem in music sound quality is at the mastering stage.
Absolutely - and this is why the Pono is not just a music player, but a service which will be selling albums that have really good mastering without the compressed dynamic range most releases have today.
There's some small benefit to increasing resolution from 16-bit to perhaps 18-bit theoretically as the ear can hear a full 120dB of dynamic range, but there's two problems left.
Yes, but if you are using PCM, the lowest bits are a long way from being full resolution.
Here is a -90dB sine wave represented in 16-bit, on state-of-the-art equipment:
And here is a -90dB sine wave represented in 24-bit:
DSD (1-bit) does not have this problem, but has other issues to deal with which make it less desirable than high res PCM.
Now of course -90dB is an extreme example, but it illustrates why 24-bit is actually better than 16-bit, even in ranges that 16-bit should be able to represent. (undithered 16-bit should have 96dB dynamic range)
I believe headphones are the number one cause of hearing damage short of something like being around gunfire.
Headphones themselves are not the problem, the problem is using open headphones or earbuds at really loud volumes to try and block out external noise.
A good pair of sealed headphones/IEMs at reasonable volume levels will not damage your hearing.
The real reason is that most of the "high definition" formats out there like SACD or DVD-Audio *SOUNDED BETTER* is that the music companies created another MASTER (i.e. re-mixed the album to sound good rather than sound LOUD on radio, etc.) for that format. So yes, that version sounds much better on a high end playback system, but it has NOTHING to do with the SACD disc itself.
Yes, but if the only way to get that master is to buy the high definition format, then you have no choice.
As for AAC, it has been proven in double-blind testing to be completely audio transparent at the 256-bit rate. I've compared it myself with lossless, CD and 256 AAC versions on my ribbon speakers and I have yet to hear a difference due to encoding in AAC.
AAC
sucks. I have ABX'ed lossy and lossless formats again and again, and I can do 20/20 in the foobar comparator standing on my head.
One of the problems that most people don't realize is that when you compress to a lossy format, you need to reduce the volume or else you are going to have intersample clipping.
Even if you reduce the gain before encoding, and level-match the test, I can easily ABX AAC and ALAC.
Another blast from the past..
You should look up the old iriver players.