[Nexus 7 General] GedBlake:
Hi, hodak...

Much of your post doesn't mean much to me I afraid... although I do remember reading years ago, that DAC stands for Digital-to-Analog Converter and FLAC stands for Full Lossless Audio Codec (I think)... but that's about the limit of my knowledge concerning technical digital audio related stuff.

With regard to "flash to a new kernel that is USB DAC friendly". I have no idea if such a kernel exists. But if one does exist, it will almost certainly be in .ZIP format (which, by the way, you don't unzip), and would be flashed via a Custom Recovery.

There are two such Custom Recoveries available; ClockWorkMod Recovery (CWM) and The Windows Recovery Project (TWRP). They both do pretty much the same thing... with such a Recovery, you can flash Custom Kernels, Custom ROMs, root your device, and perform Nandroid backups (which are 'carbon copies' of your Nexus 7's state at the time the backup was made... even right down to the last app icon or widget you last dropped onto one of the home screens). Nandroid backups are extremely useful for returning your device back to it's last working state, in the event of a ROM (or kernel) flash gone wrong.

If you've never used a Custom Recovery before, you're probably wondering which one is 'best'. Well, the answer is a rather unhelpful 'neither' :). Like most things Android related, it's very much a matter of personal taste. CWM has been around for years, and is favoured (mostly) by Android old timers:). TWRP is the new-kid-on-the block, so to speak, and has a more intuitive interface than CWM, so I guess I would recommend TWRP as this is your first foray into Custom Recovery related stuff. Anyway here are the download links...

(It's important you get the right version for your device, so if you have a WiFi only Nexus 7 (as you do), you're going to need the 'grouper' Custom Recovery...and 'tilapia' Custom Recovery, if your Nexus 7 is both WiFi and 3G capable. Download the correct one to your PC.

TWRP for 'grouper'

CWM for both 'grouper' and 'tilapia'

But before you can fastboot flash a Custom Recovery, you must first unlock the bootloader on your Nexus 7 (and this is the bit you're not going to like so much)... unlocking the bootloader, performs a full wipe akin to a factory reset. So before proceeding you must first back up everything that is important to you on your Nexus 7 to your PC or some other external location.

However, none of this might be necessary!:):).

In your post you say "...and the seller stated that it has been rooted.".

Unless the seller rooted the device via the

motochopper 'exploit'

then there's a very good chance the bootloader is already unlocked... which means you won't loose your stuff:):). If there is an unlocked padlock symbol at the bottom of the screen, underneath the Google logo at boot... it means the bootloader is already unlocked.

So, to summarize...

* Backup your Nexus 7. (Might not be necessary if the bootloader is already unlocked).

* Unlock the bootloader with fastboot oem unlock (Might not be necessary...).

* Fastboot flash a Custom Recovery with fastboot flash recovery custom_recovery_filename.img

* Using that Recovery, flash your Custom Kernel.

* Restore your stuff back to your Nexus 7. (Might not be necessary...).

To reiterate... if the bootloader is already unlocked, then only the third and fourth steps listed above are necessary.

The full details of how to use fastboot and a link to the necessary drivers are available

here

. It looks more complicated than it actually is... but that's only because Comminus (the OP of the thread) is thorough in his explanation, and covers a lot of ground.

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One other possibility occurs to me... If you're already rooted, you can use either one of these two apps...

Flash Image GUI

or

Flashify

.

...you can use one of these two apps, to flash a Custom Recovery DIRECTLY FROM THE NEXUS 7 itself, without recourse to a PC or the need for fastboot. Just download the Custom Recovery .img file from one of the links above, directly to your Nexus 7... and then use either Flash Image GUI or Flashify to flash it.

Once you have CWM or TWRP installed, you can then download, directly your Nexus 7, the Custom Kernel of your choice... boot into CWM or TWRP and flash it.

How to boot into your Custom Recovery

Shut down the Nexus 7 completely. Press and hold VOL-DOWN... whilst holding, press POWER ON (hold both for about 5 seconds). This will boot the device into the bootloader. Using the VOL-BUTTONS, navigate to the RECOVERY MODE option, and press POWER ON to select. Your Nexus 7 should now boot into your previously installed Custom Recovery... CWM or TWRP.

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And that's the Cliff Notes/Reader Digest version of how to flash a Custom Kernel. All you have to do now is find one that fits your digital audio requirements... and that, I'm afraid, I can't help you with:(... unfortunately.

Hope this helps... and good luck.

Rgrds,

Ged.