twoodland Said:
"Macbook Air won't detect external microphone: No - it doesn't show up in System Report :("
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OK - So, that shows what it is not working.
Try the Following:
- Reset the SMC and your NVRAM in Safe Mode
Reset the SMC and then NVRAM once more, but this time in Safe Mode. Sometimes when changes are made to the system(updates), system configurations (i.e. for Ports) become manipulated, technically. So, reset the SMC and NVRAM. It might take up to 3 attempts to reset each. So, be certain you have the time to so. To boot into Safe Mode, Hold Down the Shift Key upon boot. Once at the login screen, release shift. See if it all now works. In Safe Mode, only necessary items load (i.e. the caches), and new preferences are set aside.
What happens when you create a new user? Does it show up? If so, it is probably something misconfigured in you current user.
- Use a Different Computer:
See if another computer is successful. If so, then it is probably this Microphone.
Then, Scan your Mac for Malware:
Use MalwareBytes for Mac --- This is software that searches for malware/adware. So, scan with it and then remove what is found from the quarantine. Once removed, uninstall MalwareBytes for Mac. Then restart the Mac.
Downloads:
- Malwarebytes Anti-Malware for Mac
- Malwarebytes Uninstaller