HEadphone buzz in one channel

This isn't a dslr question -- it concerns audio monitoring from a Canon Vixia camcorder.

Audio is "ok" (awful but good enough) coming from the camera's internal speakers. Good enough, that is, to let you know you did record the audio - not good enough, of course, for anything else.

Today, I elected to listen to the audio on headsets to get a better sense of quality and discovered that there was lots of hum/buzz (and no other audio) in one channel, the other channel works ok. This happened using three different headphones so I don't suspect I have a broken headphone.

I used a stereo mini plug plugged into the camera's headphone jack. Same kind of plug used on a iPod

ANy idea what may be going on here.thnx
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joel albert