-24db Precut Sound Quality on Rockboxxed iPod?

[saratoga]

If that is true, digital signal received by DAC will be upscaled from 16-bit to 24-bit, then the volume control will compress/normalise according to the volume level specified.

I've already explained to you why this is not the case.  Are you not reading what people are saying, or do you really not understand what is meant by "analog" and "amplifier"?

Allow me to try again:  normalizatin and compression are not involved.  Volume control is handled purely through analog means using an amplifier.  

Thus I can derive that volume level below 100% and above 25% DOES NOT AFFECT the compression of final output.

This doesn't mean anything.  Its just a collection of nouns and verbs without content or information.

Don't get me wrong, the Wolfson DAC chip still compresses dynamic range of received signal according to specified volume level

More meaningless babble.

but it already upscales the signal to 24-bit internally (16-bit data in 24-bit channel), leaving 8-bit of interpolated fidelity.

Just stop.

I must admit though that my understanding on electrical engineering & audio manipulation are limited,

You don't say.

Reply to saratoga: I think iPod does have an amp but is set at static level (which volume can't be increased or decreased).

You think wrong.

iPod relies on digital volume on its DAC which results in dynamic range compression (less fidelity/clarity).

1)  No
2)  What part of the following sentences did you not understand: "Dynamic range compression is a type of DSP effect that you can apply to audio.  It is not a metric.  It does not determine anything.  Its not relevant here."

[Febs]

"Dynamic range compression" takes all signal above a certain threshold and reduces it by a specified ratio (this is typically called limiting) or takes all signal below a certain threshold and raises it by a specified ratio (this is typically called compression).  So let's say you have  piece of music where the highest peak is at 0 dB, and the lowest part is at -30 dB.  That piece of music would have a dynamic range of 30 dB.  Let's say you apply limiting so that the highest peak in the music is now at -10 dB and the lowest peak is at -20 dB.  THAT is dynamic range compression.  You have changed the music so that there is less of a difference between the highest and the lowest values.  There is now 10 dB of dynamic range in your music.

Now, suppose you take that same piece of music and raise every sample by 10 dB, so that the highest peak is once again at 0 dB.  You haven't changed the dynamic range of the music.  You've simply scaled the volume at every point in the file by a constant.  That is normalisation.

Now, let's say you put that file on your iPod and play it.  You turn down the pre-cut.  Rockbox scales the gain of the file by a constant.  There is still 10 dB of dynamic range in the file itself, but every sample in the file is played back at a lower level.  The effective signal to noise ratio may be lower, but the dynamic range of the music itself is still 10 dB.  The music is not "compressed" by lowering the volume.

[Bagder]

Let me just say that I don't understand half of what you're talking about, but I'm enjoying every single word here.

Go go go! :-)