Best HD File Format?

ALAC (that I use) is also compressed.  Format makes difference only if your method of delivery affects timing of the DAC, for instance S/Pdif.  When you use WiFi, Ethernet or async USB format doesn't matter since music is delivered as data.  In fact nothing on the side of computer matters (computer speed, type of HD, amount of memory).  Playback program also doesn't matter as long as it is bit-perfect (doesn't upsample etc.).  Electrical noise from computer can always affect sound of your DAC.  Because of that I selected WiFi, plugged computer into different outlet (on different phase) and use conditioner for my Airport Express, DAC and Power Amp.  Airport Express jitter still matters, but my DAC suppresses it.  If not for the distance form my computer I would go with Ethernet or async USB.

Order the same song in each format and decide what sounds best to you.Just a thought.

WAV is probably the best file format because it's raw PCM.

AIFF and ALAC are Apple's codecs and contain raw PCM as well, but not all software sill support this.

FLAC is an algorithm that compresses the PCM data to reduce the file size.  However, the core PCM data is still full resolution and uncompressed.  Some software/players will not perform as well with this format because the player will have to dynamically uncompress the FLAC file on the fly before it sends it to the DAC.  Think of this as a compressed ZIP file.  All the data is there, but it needs to be uncompressed and re-arranged before you can us it.

If you use a computer and Jriver as a player for the Brooklyn DAC, you won't have any problems.  I could not comment on other solutions - they may be fine or they may have a slight performance degradation with FLAC.