I test sound output from smartphone to record them through line-in on my computer. I have two different scenarios:

  • the phone has jack output: I have a jack male cable to connect the phone to my computer and it works fine
  • the phone has no jack: in that case I use a USB to jack adapter with the same jack cable as in the previous scenario but I don't get any sound. If I plug a headset instead of the jack cable, I can hear the sound without any problem.

I'm a bit puzzled because the USB to jack adapter works fine when using a headset but when using another the jack to line-in cable, there is no sound (line-in volume on my computer is at 100%). I have tried this on 3 different phones from 3 different brands (but all Android base) but it doesn't work.

Am I missing something?



2 Answers 2


What you are missing (it bites us all at time) is that there are no standards for this. Or to be a little clearer, there are different ways the connectors are done and they are not always compatible.

My guess is that the problem you have is with the difference between TRS cables and TRRS cables and more specifically with how the ground and mic connections are done. (Try googling trrs cable to become more confused).

Personally, I have a bunch of adapters and simply try them until it works.

  • thanks! They're both the same. My headset has a TRS jack, my cable to Line-In has also a TRS jack. Headset works fine but Line In gets no sound, I don't get it. I'll try to find another cable to see if there is any difference.
    – Laurent
    Apr 30, 2021 at 8:47

The USB-to-jack adapter might autodetect whether it is connected to a microphone or to a headset by measuring the resistance. Your computer's line-in port might have a high enough resistance that the USB-to-jack adapter may decide it is dealing with a microphone, expecting to see some signal there rather than sending something there.

One solution may be to use a headphone splitter like those used for sharing earplugs on a single phone and then connect an actual headphone in parallel with your computer's line-in. That should provide enough of a load for the USB-to-jack adapter to decide it is used as an output.

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