Jan 18, 2022
I have an audio setup consisting of two soundcards:

First soundcard:
  • Line out (lime green), for my speakers
  • Mic in (light pink), for my external microphone
  • Line in (light blue), to plug my phone in and listen to its audio from my PC speakers without disconnecting them

Second soundcard:
  • Line out (lime green), for my headset output
  • Mic in (light pink), for my headset input

I checked the "Listen to this device" option for my line in (first soundcard) and I just leave the jack unplugged when there is no need to connect my phone.

Everything works fine by itself, except for whenever I try to connect both the mic in and line in of my first soundcard at the same time: they act as if they were the same device (which device depends on the one I plugged in first), so it happens that either I get an infinite feedback loop from my microphone (treated as line in) or I cannot hear my phone (treated as mic in).

Is it possible that my soundcard only accepts one input at a time?

If so, how can I plug all my three inputs in at once without buying a new soundcard?

P.S. I tried with softwares like VoiceMeeter but they to not help: it seems to be a lower level issue.

I hope I was clear. Thanks in advance, Simone.
Last edited:


Make and model phone?

The problem could be the combination of ports and plugs: TR, TRS, TRRS. (Tip, Ring, Sleeve).

There are standards but there are also variations. Apple, uses a different configuration.



Take a close look at plugs and ports.

There could be a mismatch.

Especially in a mixed environment of headsets, microphones, phone, audio cards.
Jan 18, 2022
Thanks for your answer.

I checked the male jacks and they are all TRS.

As said, when I connect my devices one by one there are no problems: they start to conflict as soon as I plug my mic in and my line in at the same time.

My smartphone is a Xiaomi Mi 9T Pro.


Perhaps the following link will help....


Google "can I use mic in and line in together"

You can easily find similar links.

No specific answer to offer. However, depending on the hardware (and perhaps software) the sound card may be acting just as it was designed to do.

Recognize the first device plugged in and ignore the second device in some manner.

Could be some built in safe guard to protect the audio card. Or devices connected to it.

In the meantime I am going to move your post from Components to Home Audio.

Hopefully a couple of the resident audiophiles will be able to offer additional suggestions and comments.

Or correct some error of omission or commission on my part.
Jan 18, 2022
Thank you again.

Your link explains the difference between line in and mic in, which is not very useful in this case.

I tried to Google the search keys you suggested and the only useful piece of information I managed to find was this reddit, which suggests that a soundcard could possibly treat the mic in and line in signals as a unique stereo output ("hi and low level",).

In this case, is it possible to split them later?