jamsession
Member
I got some 24 conductor (12 twisted pairs) cable here that has an overall foil shield and braid, but not individually foil or braid shielded. If I use that for a school project I'm working on (low-budget, but I want to do a time and resources-balanced job for a production of "much ado about nothing" next week), and have 6-18" fanouts on them, do I need to wrap each in foil and add braid on those 12-18" fanout ends?
I know it's dependant on the amount of EMI, RFI energy in the area (audience cell phones, wireless mics, interplanetary alien communications, sunspots, etc etc.)
AND it’s a _bugger_ to rework if I get it wrong
AND that's why they make individually shielded snake cable (does your snake cable have separate foil and braid also? Most don't for size considerations, it looks like individual foil and overall foil/braid is common?
But I'm looking for real-world advice - if I'd probably be ok with the fanout ends exposed 1 foot if the rest was overall shielded well
Do you have any references for proper real-world shielding? It’s a fascinating field of study. (Kind of like making CAT5 lan cable, the specs say it's ok to unwind the twisted pair for 3/4" or so when adding the connectors and still stay in spec.) So all shielded cables are unshielded at the XLR pins for 1/2" or so, and curious how the physics work, I know it's a good better best scenario, and hum is a B&^TCH, but individually foil wrapping and braiding 18" and shrinkwrap over them is a lot of work too. I have this otherwise great cable and will use it on this job since I'm donating my time and labor for the most part, just want to get it done as well as reasonable in the time I have, and put the right amount of effort into it, if this cable should work ok.
This is for balanced XLR runs. If I was running unbalanced, shielding would be even more important, right? (that's why we DO balanced to remove at least certain types of interference). I wish I could see pictures of shielding in action, esp. shielding effects of balanced vs unbalanced lines, and diff types of interference. EG: How much intererference would get into 1" unshielded cable, 6", 18", 20'. Plus points to anyone who shares links to that!
fyi - whirlwindusa.com has lots of neat boxes - isolators and balancers, would love to hear experiences with those or similar products.
Sub-Question:
(would welcome stories of sources of hum not including your humming, "I'm on the top of the world" on the way to work. :^) and solutions to fix them.
My recent hum story:
Got the stage all miked proper, and when the wonderful stage hands put the podium out for the keynote speaker, with the AC powered green desk lamp out there (aquired an hour before the show), desk mic stand with an SM58 pointed right at it... you can see where this is going. Yep, picked up a beautiful 60 hz hum. Now I get to help the videographer take that out in post. Since he and the client didnt' notice it, I wonder if I should bother. Uggh. another thing to add to the preshow checklist. Anyone use LED podium lights? the green desk lamp was so bright through the green plastic "lampshade" that it threw off the exposure from the speakers face. another Uggh. that lamp is history as soon as I find a better alternative. I could put an LED bar in there. Gotta love LED lighting.
Cheers,
Jam
I know it's dependant on the amount of EMI, RFI energy in the area (audience cell phones, wireless mics, interplanetary alien communications, sunspots, etc etc.)
AND it’s a _bugger_ to rework if I get it wrong
AND that's why they make individually shielded snake cable (does your snake cable have separate foil and braid also? Most don't for size considerations, it looks like individual foil and overall foil/braid is common?
But I'm looking for real-world advice - if I'd probably be ok with the fanout ends exposed 1 foot if the rest was overall shielded well
Do you have any references for proper real-world shielding? It’s a fascinating field of study. (Kind of like making CAT5 lan cable, the specs say it's ok to unwind the twisted pair for 3/4" or so when adding the connectors and still stay in spec.) So all shielded cables are unshielded at the XLR pins for 1/2" or so, and curious how the physics work, I know it's a good better best scenario, and hum is a B&^TCH, but individually foil wrapping and braiding 18" and shrinkwrap over them is a lot of work too. I have this otherwise great cable and will use it on this job since I'm donating my time and labor for the most part, just want to get it done as well as reasonable in the time I have, and put the right amount of effort into it, if this cable should work ok.
This is for balanced XLR runs. If I was running unbalanced, shielding would be even more important, right? (that's why we DO balanced to remove at least certain types of interference). I wish I could see pictures of shielding in action, esp. shielding effects of balanced vs unbalanced lines, and diff types of interference. EG: How much intererference would get into 1" unshielded cable, 6", 18", 20'. Plus points to anyone who shares links to that!
fyi - whirlwindusa.com has lots of neat boxes - isolators and balancers, would love to hear experiences with those or similar products.
Sub-Question:
(would welcome stories of sources of hum not including your humming, "I'm on the top of the world" on the way to work. :^) and solutions to fix them.
My recent hum story:
Got the stage all miked proper, and when the wonderful stage hands put the podium out for the keynote speaker, with the AC powered green desk lamp out there (aquired an hour before the show), desk mic stand with an SM58 pointed right at it... you can see where this is going. Yep, picked up a beautiful 60 hz hum. Now I get to help the videographer take that out in post. Since he and the client didnt' notice it, I wonder if I should bother. Uggh. another thing to add to the preshow checklist. Anyone use LED podium lights? the green desk lamp was so bright through the green plastic "lampshade" that it threw off the exposure from the speakers face. another Uggh. that lamp is history as soon as I find a better alternative. I could put an LED bar in there. Gotta love LED lighting.
Cheers,
Jam
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