Originally posted on RAMPS ---> http://groups.google.com/group/rec....bac6dcd8c1/b80c2df620cc731b?#b80c2df620cc731b
********************
Hello,
I've got an audio puzzler for you here;
Been surfing this board more than usual the past couple days gathering
all kinds of useful tidbits and came across one discussion (regarding
XLR wiring; specifically, the pros and cons of connecting pin1 to the
XLR shell) that sparked my curiosity about a problem I had earlier
this year.
I was bag mixing for a doc on slam poetry and we're setting up for a
nice, relaxed walk n' talk shot down North St beach here in Chicago
and all of a sudden it seems that my boom pole has turned into a
veritable hum magnet. The hum sounded like a messy version of 60cycle
and would vary in amplitude and abrasiveness with movement of the boom
in different positions.
Maybe someone with a little more electrical wisdom than I can explain
what was happening here.
Factors to consider:
- I was right on the lake shore (lake Michigan)
- It was a cold, wet, drizzly sort of day
- I had clear line of sight to the John Hancock building <1mile south
of my position (massive antennae tower)
- The footing was a mix of wet cement and wet earth.
Equipment/Signal Flow in use:
416 T-Power ---> Shorty XLR jumper (pin1 connect to shell both ends)
---> vdb coil cable pole (pin1 NOT connected to shell) ---> Boom to
Mixer XLR jumper (pin1 connect to shell both ends) --->PSC Alphamix
Other factors:
- When the camera op broke to do B-roll and switched on his camera
mount shotgun (P48) there was no hum on the recorded sound.
- Even with no cables plugged into the Alphamix I could still hear a
bit of the same hum in the noise floor.
- I had wires (lectro 200 series) on the subject and interviewers and
vaguely remember having the same problem but to a much lesser extent.
My best guess:
-From what I just read on an old posting it sounds like T-Power mics
don't like cables that have the shield tied to the connector shell,
something about the signal being present in the shield as well as
pin2. So maybe I inadvertently created an RF antennae and somehow the
416 was amplifying the noise?
-Maybe the coiled cable of the vdb was inducting noise?
-Or maybe (really hoping this isn't the culprit) the PSC Alphamix is
just not well designed for RF immunity.
Hope someone has the time and interest to clue me in on this one! It
really made a mess for sound that day and I would love to avoid the
problem in the future. Thanks in advance!
********************
Hello,
I've got an audio puzzler for you here;
Been surfing this board more than usual the past couple days gathering
all kinds of useful tidbits and came across one discussion (regarding
XLR wiring; specifically, the pros and cons of connecting pin1 to the
XLR shell) that sparked my curiosity about a problem I had earlier
this year.
I was bag mixing for a doc on slam poetry and we're setting up for a
nice, relaxed walk n' talk shot down North St beach here in Chicago
and all of a sudden it seems that my boom pole has turned into a
veritable hum magnet. The hum sounded like a messy version of 60cycle
and would vary in amplitude and abrasiveness with movement of the boom
in different positions.
Maybe someone with a little more electrical wisdom than I can explain
what was happening here.
Factors to consider:
- I was right on the lake shore (lake Michigan)
- It was a cold, wet, drizzly sort of day
- I had clear line of sight to the John Hancock building <1mile south
of my position (massive antennae tower)
- The footing was a mix of wet cement and wet earth.
Equipment/Signal Flow in use:
416 T-Power ---> Shorty XLR jumper (pin1 connect to shell both ends)
---> vdb coil cable pole (pin1 NOT connected to shell) ---> Boom to
Mixer XLR jumper (pin1 connect to shell both ends) --->PSC Alphamix
Other factors:
- When the camera op broke to do B-roll and switched on his camera
mount shotgun (P48) there was no hum on the recorded sound.
- Even with no cables plugged into the Alphamix I could still hear a
bit of the same hum in the noise floor.
- I had wires (lectro 200 series) on the subject and interviewers and
vaguely remember having the same problem but to a much lesser extent.
My best guess:
-From what I just read on an old posting it sounds like T-Power mics
don't like cables that have the shield tied to the connector shell,
something about the signal being present in the shield as well as
pin2. So maybe I inadvertently created an RF antennae and somehow the
416 was amplifying the noise?
-Maybe the coiled cable of the vdb was inducting noise?
-Or maybe (really hoping this isn't the culprit) the PSC Alphamix is
just not well designed for RF immunity.
Hope someone has the time and interest to clue me in on this one! It
really made a mess for sound that day and I would love to avoid the
problem in the future. Thanks in advance!
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