[matthewpartrick]

Title says it all.  I'm a little dubious this will make a difference.  Comments?

[JLM]

i'd also like to learn more about the pros and cons of each. 

As I've read ALAC takes more storage space but less processing than AAC.  Do I have the right initials here?

[srb]

Converting AAC to ALAC will not increase sound quality but will inflate the filesize to more than double.

As far as processing power, on my Windows 7 3.0GHz Core 2 Duo computer, playback from JRiver shows CPU utilization at ~ 3% for either format.*

* Originally reported ~ 5%, but that was with 3D Cover Art 3D Spectrum Analyzer enabled.

Steve

[fiveoclockfriday]

Echoing what Steve said; an AAC file is a lossy file. Data has been thrown out to compress that file. ALAC is a lossless format. So once you already have the lossy file (AAC) there's zero benefit to converting it to a lossless format (ALAC).

[JLM]

Thanks Steve and five.

Had my Apple-speak confused.  AAC is compressed - similar to MP3 (typically used for inexpensive players or internet streaming), ALAC is losslessly compressed - similar to FLAC, and AIFF is uncompressed - similar to WAV.

But Steve my question still stands: does playback of ALAC take significantly more computing power than AIFF?  I ask because I'm in process of moving from 8 GB iMac via optical to 4 GB MacBook Air via USB and have had dropouts.

TIA

[srb]

But Steve my question still stands: does playback of ALAC take significantly more computing power than AIFF?  I ask because I'm in process of moving from 8 GB iMac via optical to 4 GB MacBook Air via USB and have had dropouts.

I see that you are using iTunes, so this last comparison was done in iTunes, albeit on the Windows platform, and of course using iTunes as the playback engine (versus using an Amarra, Pure Music or similar playback engine plug-in as one might do in iTunes on the Mac).

Using a 16-bit/44.1KHz AIFF file and an ALAC conversion of it, the CPU utilization was:

AIFF:   1.4%
ALAC:  1.6%

The ALAC took a tiny bit more CPU, but hardly enough difference to matter.

You say you are getting some dropouts on the MacBook Air via USB.  Are you comparing AIFF and ALAC on that platform and only getting dropouts with the ALAC versions?

Steve

[JLM]

Sorry for hijacking the thread, but....

Thanks again Steve, sounds like that consideration can be put to bed.

All testing of USB cables with ALAC, results vary depending on the cable (the more expensive filtered cable was by far the worse for dropouts but sounded the best) and USB port used (right port trends better).  Does not vary by which USB setting used on the DAC (2.0 vs. 1.1).  I'll publish full results when the rest of my samples arrive for home audition.

For the purposes of comparison, is there such a thing as break-in for USB cables?

[matthewpartrick]

Thanks guys, that's what I figured but just was making sure I wasn't missing something.