Just bought a Mac Air (2012). It has only one audio port, but it is supposed to accommodate an external mic. From what I've researched, the port will accept TRRS jacks only. I can't get my Mac Air to recognize my mic. I have a Sure M57 mic plugged into a tube amp. There is a line out from the amp, which is a chord with a 1/4" jack. This is plugged into a 1/4" to 1/8" adapter, with the 1/8" (3.5mm) jack being TRS. The male end of this adapter is plugged into another adapter, with this second adapter's male end being TRRS, which is then plugged into the Air's audio port. End result, the Air does't recognize the mic. I'm thinking that the TRRS adapter I'm using (StarTech) has the 'ground' and 'mic' section of the jack reversed from what the Air's audio port can accept. I haven't come across any information to confirm this. Has anyone had a similar experience? I have seen the iRig adapter (1/4" to 3.5mm TRRS) used in a new Mac Air at the Apple store, and the Air recognizes the adapter by showing 'External Microphone' in the Audio section of the System Preferences. But the iRig is $40, and the StarTech adapter I bought was $8. The Apple tech person said to check out this website for help, so here I am. Any help would be greatly appreciated. Thanks!
Maybe try a 3.5mm camcorder AV cable. It will have a TRRS on one end, and break out to 3 RCA jacks on the other. Then use an RCA to 1/4" TS adapter on the appropriate RCA jack to plug it into your mic pre.