Hi, and welcome to the forum. I moved your thread to the Multi-Channel Musicians Studio section.
I don't know what bit rate/KHZ you are recording at, but 24 bit / 96 kHz would be good. But however you record, AC3 is a "Lossy" format. Better to go with a "Lossless" format like Flac. But understand sometimes one has to go with what one has or need, depending how one can play back Multi-Channel. AC3 is used for regular DVDs, but if you are playing files back on computer and want to save space and still be "Lossless," go with Flac. Foobar 2000 is a free PC program that will playback just about everything in Multi-Channel.
Hope this helps.