How to output sound from two sources to one headphone?

Question

Electronics

Greetings, you need to output sound from two USB devices (audio card and microphone) to one headphone. There seems to be a way - an adapter-splitter, but I read on the Internet that it is dangerous for the equipment . Actually, the following question appeared: why is this connection method dangerous?
I do not consider other ways, such as buying a mixer and other expensive equipment

Answer 1

Because the output of source A goes to the output of source B, and if the phases of the signals fail to match, there will be a “who is stronger” pull, which will definitely ruin the sound, and theoretically, it can burn one or both devices.
In short, buy a mixer on Avito.

Answer 2

there are schemes on passive elements, but such mixing of powerful signals is not effective.
like this, keep in mind the circuit is not for a stereo signal.

Answer 3

It is dangerous because both sources are active and, under favorable conditions, will burn each other. Therefore, electrical circuits are needed to prevent the signal from getting from one source to another - switcher mixers.
And in your case, if you correctly specified

from two USB devices (audio card and microphone)

and you really have a USB microphone, then you need a software mixer - which is inside the computer and will reduce the signal from the microphone card and audio player / sound recorder and feed the usb sound recorder to the output

Answer 4

and turn on the soft mixer is not destiny?
there is nothing dangerous in such a connection, who
told you these horror stories?

Answer 5

Connect the microphone output to the audio input and programmatically mix two signals to the headphone output of the sound card.
In Windows, this is a regular function for the microphone, it is turned on with one checkmark in the settings.