Inspiron 17 5748 does not recognize external microphone
I have an Inspiron 17 5748 that I upgraded from Windows 8.1 to Windows 10 some time ago. I have never used a headset with it, before or after the upgrade, until recently. My issue is that the system does not seem to recognize the external microphone of the headset at all.
Some background... the integrated microphone and speakers work fine. If I plug headphones into the audio jack (it is a single combination jack), they automatically cut out the speakers and also work fine. If I plug in a headset, the headphone portion works fine but the microphone is ignored. The integrated microphone continues to pick up sound. I made sure that neither the headset hardware nor the speaker selection was muted.
In an effort to localize the problem, I tried the headset (a Logitech h151 with a 3.5 mm plug and four contacts) in my iPad, and the microphone works fine there. I checked the laptop documentation, and it says you can plug in just a headset, just a microphone, or a combination, so I tried an older headset I had that contained two plugs, one for the headphones and one for the microphones. The headphones work fine, but the microphone is ignored. (Of course, it was necessary to try the plugs one at a time.) I also tried a Logitech h540 USB headset, with the same results. The Logitech tech support person told me that they do not recommend the H540 for use with Windows 10, but then relented when I pointed out it was listed as compatible on their website. She then concluded the h540 was defective, but recommended the h151 anyway.
If I go to Sound, Recording Devices, the only microphone listed is Realtek High Definition Audio, regardless of whether or not I plug in the headset. I have uninstalled and reinstalled the Realtek driver with no change in the outcome.
I have found some internet comments for similar problems indicating that an "IDT High Definition Audio Codec" should appear on the above list, but I don't know if that is for a specific, alternative audio board and whether it would apply in my case.
Any help or advice regarding resolving this issue would be greatly appreciated. Many thanks!