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Some time ago, I decided to upgrade my audio from simple headset to Studio headphones and a condenser mic. For the longest time I used a XLR-1/4"Jack Mono to plug it into my Soundcards LineIn. I've recently started to record with Nvidia's ShadowPlay, and unlike Teamspak/Discord/Skype/etc. my voice did only get recorded on the left channel. So I changed the cable from the AMP to a XLR-1/4" Jack Stereo. Now I get proper stereo in Audacity and even Sykpe. But any application that seems to do a downmix to mono will not pick up any sound. I can especially see that in Voicemeeter, when I manually select mono for the LineIn input. Of course Voicemeeter is a solution, but I don't want to use a software solution if any way possible.

1: Microphone Amp ,

2: Sound Card

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  • I can't resist: there is a reason why they call it a mono application. :)))
    – eckes
    Commented Jul 16, 2017 at 12:55
  • But then what is the reason that when I select Wave as a input for Teamspeak, It works just fine - even delivering full stereo? There seems to be more to this than your simplification.
    – Cetuximab
    Commented Jul 16, 2017 at 13:34
  • I was kidding, really. The smiley should have given it away.
    – eckes
    Commented Jul 16, 2017 at 14:15
  • Quick test... record the mic in Audacity. Bounce the resulting stereo track to mono - what do you hear? If it sounds normal, then we need to look elsewhere, but if it goes silent or very quiet, you have a phase problem with your input jack.
    – Tetsujin
    Commented Jul 16, 2017 at 15:29

1 Answer 1

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Studio mics with XLR plugs use differential signalling: the mono signal is transmitted on two lines with opposite polarity. That way, crosstalk and interference is reduced.

If your soundcard line-in records those two lines as two stereo lines, it's still not really a stereo signal, it's a (differential) mono signal.

The proper way to convert it to mono (if your soundcard can't be switched to differential XLR inputs) is to negate one channel and add it to the other channel, that will remove the crosstalk and interferences. If you can't do that, the next best thing is to use just one channel ("my voice did only get recorded on the left channel").

If you want to convert the mono signal to stereo, the proper way is to copy the signal from one channel to two channels, possibly with different factors or delay so that it seems to come from the direction you want it to come.

What you've been doing so far (record both channels as stereo) is the wrong way: The polarity on one channel is inverted, and that will give the wrong directional effect.

That's also the reason that applications that downmix stereo to mono will not pick up any sound: As the polarity is inverted, the signals cancel each other out.

So:

  • the only hardware solution is to set your soundcard to accept differential XLR input, if it can, and give you a true mono signal. If that doesn't work:

  • all other solitions are really software solutions, properly inverting, downmixing and then upmixing the channels.

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