How can I get a balanced stereo signal from an external mic in Keynote?

I’m trying to record a voiceover - with an external Samson CO1U - USB Studio Condenser mic - to a Keynote presentation on my MacBookPro MacBook Pro (Retina, 13-inch, Mid 2014) before exporting it a video file. The problem is, that the audio is confined to the left channel.

I have tried altering the balance using Audio MIDI Set-up but that doesn’t work. I need to use the external mic to get a better sound quality than using the MacBook’s internal mic.

Is there a way to get a balanced stereo (or split mono) signal from an external mic?

You could use something like Audio Hijack to record directly to mono, or mix down the file in something like Audicity.

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Microphones generally are mono, and only produce a single channel of audio. You should be able to pull it into GarageBand (or any other DAW) and export a file from there. Just balance the microphone track dead center in the stereo mix first.

Thanks chaps. The recording has to be in Keynote because it’s a voiceover and timed to slide changes and animations. How can I take the audio track out of Keynote, then edit in say Audacity and THEN add it back to the Keynote file?

The problem seems to have arisen in the past with a different USB input devices.

I just checked my USB input headset and it has no control for L/R inputs. I use Camtasia and have no problems with it. Camtasia automatically merges and rebalances the L with the R.

Here is an old thread on how to find the audio track from a Keynote presentation.


Many thanks. I’ll give that a go.