I need a way to make apps use the second input line from USB sound card. By default the all use input one. Does anyone know how to split the two input channels into two separate devices or alternatively merge the to inputs into one input channel?

It seems like OS X is treating the two channels as one Stereo channel instead of two separate inputs.

Background information

I have a lexicon Alpha sound card. It has two input lines, The first for instruments and the second for a microphone. I'm able to see both lines in audio MIDI setup. If I go into the system preferences I see both lines as one input device and I can see the sound bar move if I speak in the microphone or put jack table in the instrument plug.

If I use Skype or dictation or hangouts or any other normal app only the instrument input is used. If I use Audacity the input is recorded as one stereo channel with the instrument on the left channel and the microphone on the right channel only.


1 Answer 1


In Audio Midi Setup, you may have the choice of which is the primary input in non-ASIO applications…

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Alternatively, it might be possible to rearrange the inputs if you use an Aggregate device

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I've only used Aggregates for testing, experimentation, so I'm no expert - but it appears you can renumber the channel order by clicking the individual channels in the top section.

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