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Sound Grabber II loud hum w/ 2 Canon camcorders w/ AC/DC power or AV line out


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#1 cs303

cs303
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Posted 22 May 2010 - 01:09 PM

With a new Sound Grabber II connected to either of 2 Canon Camcorders, an FS200 Flash Drive, or a ZR500 DV, it produces a very loud hum only:

1) when the camcorder is connected to its external Canon AC/DC power supply, with no other external devices than the Sound Grabber II to mic in, or

2) the camcorder is on battery power, and connected only via the AV out port to an AV system

When either camera is running on its own battery power and not connected to any other AC powered devices, there is no hum with the Sound Grabber II.  

The hum is loud enough to almost drown out all other sounds, including normal or loud speech.  

Both camcorders record without hum using an external Sony ECM-MS907 mic, or internal mics, with or without AC/DC power or AV out cable to an AC device.  

I have read all the posts here about the Sound Grabber II, and researched hum and ground loops, and haven't found this, except with a different Canon camcorder,
Ground Mismatch in All Things Audio - post 5

Tested mono/stereo plugs - suggested in another thread - same results.  Tested two Canon AC/DC power supplies - same results.  Tested other AC circuits, same results.  

Recording loud sounds - placing the mic on a table radio, the hum decreases greatly but doesn't disappear - returns as soon as the sound levels drop. This is without any auto-sound feature enabled on the camcorders - but they must have auto gain active with external mics.  

I have not tested the Sound Grabber II microphone on other devices.  The AAA battery in the mic is a Panasonic industrial, and tests strong.  

We would like to begin recording small meetings later this week, and want to use the Canon AC/DC power supplies, since the batteries won't last long enough.  Alternatives are the internal mics.

Suggestions?  Could there be a harmonic interference between the electronics in the mic and these Canon camcorders causing this loud hum?