On Tue, 18 Feb 2003 22:36:01 -0700, newvideo@amug.org (Bill
Davis) wrote:
>> >In that mess of cabling is a 25-foot extension
cable with 1/8" jacks. If
>> >I place the extension right at the beginning, I
don't get hum, but if I
>> >put it at the camera end, I do. I guess it makes sense that if the pad is
>> >toward the end of the chain, the noise gets
attenuated as well...
>Bingo.
>
>Congratulations, you've just created a 25 foot RF
antenna and plugged it
>directly into your camcorder.
>
>Also, by combining the two parts of a stereo board feed
with "Y" adaptors,
>running them through a mono component (the attenuator)
and spliting them
>back into a stereo pair, you're likely to face a nasty
little mess of
>phase cancelation at some point.
>
>If you're going to do this regularly and want good
results, it's time to
>spend a bit of money.
>
>Buy one of the XLR to camera adaptors (like the Studio 1
or the Beachtek)
>and run balanced cables from the board to the adaptor.
The short
>unbalanced run from the adaptor to the camera will be a
zillion times less
>susceptable to noise than the way you're doing it now.
>
>Good luck.
Having done a lot of single-sided long-line audio recording
work in my day, I do not think the 25' extension cable is
a problem if it is properly shielded (it was likely
unshielded headphone extension cable, the real cause of
the problem...). Also, phase-cancellation is not really a
problem with summing channels (or mixing tracks would not
be as easy as it is...;-), assuming no phase inversion in
one
of the sources (some mics are phase-inverted, as can
be some amplification devices - and the phase problems
would exist regardless of how the tracks are combined),
but electrically summing channels of amplification devices
without series resistors can cause stability problems. And,
due to the DC-output of many camcorders, and the electronic
sensing of some of the stereo/mono condition at the inputs,
some connection methods may result in mono on only one side,
or both, of the recorded audio...