My sansa zip won’t play and recognize aac files,
I tried many versions: m4a,m4b,aac with no success
Regular aac files downloaded from the iTunes store are the only ones tested to work. If you’re encoding them yourself, you may have issues with the Zip playing them.
The Clip Zip will play AAC-LC format media from your CD collection, imported via iTunes. The HE variant is a different animal. I’ve played 256 kb/s files without incident.
The problem with iTunes is that it is optimized for the little iPod family of devices, and really, really wants to make you happy by directing you to the iTunes Store. No matter, the settings you’re looking for are under Edit > Preferences > General, then look down the list to Import CD. Click on Import Settings. By default, you can try iTunes Plus (VBR up to 256 kbps) or one “step” back, the “High Quality” setting is 128 kbps (stereo). Under “Custom”, you have the available selection for constant rate or VBR, just do NOT select the HE option, I don’t think that one works.
Well, it looks like I might just try a few options. Never used iTunes for ripping CDs, but as long as the output is the same as the purchased version, it should work. I’ll have to give it a shot, now that you have me curious.
Bob 
thanks for the replies I tried many podcasts downloaded from itune: with m4a,m4b,aac extension with no solution. I am using msc mode
The solution I’ve found to the iTunes aac problem is either: 1. Create your aac files using Nero AAC thru foobar2000
or,
2. Import your iTunes aac files into foobar2000 and use the mp4 optimizer utility.
This has worked perfectly for my 8gb zip clip and 32gb external micro sd attached. My player hasn’t had any more refresh issues or playback issues on any of my iTunes encoded or purchased aac files. I’m sure that iTunes encodes are (by design) optimized to work with iPods and Apple products.
Hope this helps. Jeff S
