1) Your HDD needs to be shared on your network as a shared drive.
There are several ways to achieve this - the cheapest being a router with external USB drive support.
If you have an existing shield and it’s left always on, I think shield should allow for enabling external drive - but you will need to check on that.
Result - This would make your file available on the network for your CCA to access
2) File transfers (or any transfers ) on a network are without exception lossless.
Imagine If network transfers were lossy - an email you send saying - “No, I do not agree” could very well turn into “I do agree”
Result - Your CCA now has access to your files in whatever format they are on your drive - i.e. lossless FLACs if the drive has FLACs
3) The last piece of the puzzle is the mechanism through which your CCA will access the files. The answer to that is setting up a DLNA server on the mechanism through which you achieved (1) above.
Again, the easiest / cheapest way to achieve that would be through a router that supports external USB support and DLNA
Having said that, it should be possible to do that on your shield too.
Result: Lossless transfer of your lossless files to your CCA - You could now either use your audiolab preamp DAC for thefinal conversion or take the analog out from the CCA.
I can’t comment on the DAC performance of the audiolab although the CCA DAC is very well regarded