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Posted by Richard Crowley on 03/26/07 20:37
"David" wrote ...
> I tried connected a battery powered external lavaliere mic (Audio
> technical ATR-35s) to my Sony DCR-PC9 camcorder via the "plug in
> power" mic - in jack. It works great when the camcorder is running
> on batteries, but when the camcorder is plugged into the AC adapter
> there is a lot of hum. (60 Hz hum, not hiss). Judging from what I"ve
> read on other sites, this is a fairly common problem.
>
> I tried various things to deal with the hum. I noticed that if I
> grounded the case of the Sony (touching the metal tripod socket to a
> water pipe, for example) the hum completed disappeared. I am thinking
> of rigging up a wire with an alligator clip so that I have an easy way
> of making the connection from the camera housing to something that is
> electrically grounded.
>
> Is there any risk of hurting the camcorder by doing this? Should a
> resistor or fuse go in series with the grounding wire so that if
> something goes wrong the current flow over the grounding wire is
> limited?
It would be a bit safer to put a 10-100 Ohm resistor in line
and/or a 1/4A fuse, etc. You can buy pre-wired in-line fuse
holders at auto parts stores, etc.
Same thing happens with laptop computers. The "wall wart"
(or "cord lump") power supplies that come with those things
are notoriously noisy (RFI noise).
I have found a similar problem even when running on batteries
with the digital hash from the flip-out viewfinder LCD screen.
Must make sure any mic lines are routed *away* from the
viewfinder LCD.
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