Just wanted to follow up that it works, and I'll leave this here for anyone else googling this question.
The setting is on this page of the app: Bluetooth input tab (bottom of screen) Mic Tab (top of screen) Mic selection set to: Earphone inline mic
I used this TRRS splitter to attach a normal mic input. https://www.amazon.com/gp/product/B07FB8LCQ7/
They're 50 ohm headphones, so you shouldn't need an amp to drive them. Something high impedance, like the Sennheiser 6xx/650 (300 ohms) would need an amp to get proper volume.
> How can I use the mic if it is a separate cable?
Get a Y-splitter. Something like this:
https://www.amazon.com/Headsets-Splitter-Separate-Headphone-Nintendo/dp/B07FB8LCQ7
If you mic has a 3.5mm jack connector, you could use this type of audio cable and plug your headset and the mic on the mixamp : https://www.amazon.com/Headsets-Splitter-Separate-Headphone-Nintendo/dp/B07FB8LCQ7/ref=mp_s_a_1_15?dchild=1&keywords=audio+3.5mm+audio+mic&qid=1597769612&sr=8-15
https://www.amazon.com/Headsets-Splitter-Separate-Headphone-Nintendo/dp/B07FB8LCQ7/ easier to see microphone jack vs headphone jack
You need the correct adapter: https://www.amazon.com/DuKabel-Top-Adaptador-divisor-auriculares/dp/B07FB8LCQ7
Post a picture of yours.
Amp is not needed. Use this cable to combine your mic and headphones into one cable: https://www.amazon.com/Headsets-Splitter-Separate-Headphone-Nintendo/dp/B07FB8LCQ7
If you WANT an amp, and live in America, then get this amp.
If you WANT an amp, and live in europe, then a Fiio amp.
If WANT an amp+dac combo, then go for Topping DX3 Pro+.
I also use an AntLion ModMic with this cable on my Xbox One controller:
If you have two jacks on your headset (separate audio and mic) then you need to get jack combo. Something like this: https://www.amazon.com/Headsets-Splitter-Separate-Headphone-Nintendo/dp/B07FB8LCQ7
I use something like this with my laptop to use a desktop PC mic. Add a 2.5 to 3.5mm TRRS adapter and it might work. https://www.amazon.com/dp/B07FB8LCQ7/ref=cm_sw_r_cp_api_i_xsFZDb5B6K6W2
I have been able to do it and would be happy to share my experience with you to save you the pain of my research...
I am using this sound card that comes with cronusmax which I plug into my ps4 https://shop.cronusmax.com/external-usb-sound-card.html
I have this trss audio splitter plugged into said sound card https://www.amazon.com/gp/product/B07FB8LCQ7/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1
There was a ton of ground loop feed back... so i had to get 2 of these plugged into the split mic and headphone ports https://www.amazon.com/gp/product/B019393MV2/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1
then plug one end into your computers microphone (ps4 audio out goes into pc mic in)
and the other end.. (ps4 audio in) goes into your pc's audio out...
for control of the audio im using voice meeter and voice mod... My headset is a wireless ps4 platinum headset with the usb plugged into the computer.. and I use a normal physical microphone rather than the platinum headset mic .. I havean old launchpad midi controller used for muting and various audio effects.
This should do the trick.
https://www.amazon.com/dp/B07FB8LCQ7/ref=cm\_sw\_em\_r\_mt\_dp\_U\_WtLUDb73AHNHP