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mcp6453[_2_] mcp6453[_2_] is offline
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Default Conductive PVC Shield

Out of curiosity, I just stripped the jacket off of a cheap microphone
XLR cable that came with an Audio Technica ATR2100 microphone. There is
a second jacket inside the outside jacket. If the cable is the same as
the one at the link below, the inside jacket is a "Conductive PVC Shield."

https://www.bhphotovideo.com/c/produ...ies_XLR_M.html

How effective is the conductive PVC shield? I assume it's crap, but can
it be quantified? Is it 50% as effective as a foil or 100% braid shield?
30%? 80%? I used one of these cables in a pinch and was surprised when
there was a little noise in the system. It will be interesting to see
whether a real cable will clean it up.

Bonus question: What's your favorite bulk XLR mic cable (other than star
quad types?)
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Mike Rivers[_2_] Mike Rivers[_2_] is offline
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Default Conductive PVC Shield

On 10/1/2018 5:44 PM, mcp6453 wrote:
How effective is the conductive PVC shield? I assume it's crap, but can
it be quantified? Is it 50% as effective as a foil or 100% braid shield?
30%?


It's just fine. The percentage that you sometimes see related to a
shield has to do with how tight the braid weave is, but since there's no
braid in this type of cable, there's no number.

If the microphone output is balanced and it's going to an amplifier with
a differential (most say "balanced") input, nearly all of the hum
rejection is done by the balanced connection. The shield helps with high
frequency noise.

Bonus question: What's your favorite bulk XLR mic cable (other than star quad types?)


Star quad is kind of a special purpose cable - good to use when you know
you're going to have an EMI problem, but otherwise better to use
something else that has lower capacitance. Belden 1800F makes good mic
cable, and it also has a characteristic impedance of 110 ohms, so it's
designed to work with AES3 digital audio connections when you want to do
it right.


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Phil Allison[_4_] Phil Allison[_4_] is offline
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Default Conductive PVC Shield

mcp6453 wrote:

Out of curiosity, I just stripped the jacket off of a cheap microphone
XLR cable that came with an Audio Technica ATR2100 microphone. There is
a second jacket inside the outside jacket. If the cable is the same as
the one at the link below, the inside jacket is a "Conductive PVC Shield."

https://www.bhphotovideo.com/c/produ...ies_XLR_M.html


** The Pearstone cable has a spiral, copper grounding shield - says so the "overview".

It also states the purpose of the conductive PVC shielding is to reduce electrostatic ( ie handling ) noise.


How effective is the conductive PVC shield?



** Very effective at the stated purpose.



..... Phil
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geoff geoff is offline
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Default Conductive PVC Shield

On 2/10/2018 4:22 PM, Phil Allison wrote:
mcp6453 wrote:

Out of curiosity, I just stripped the jacket off of a cheap microphone
XLR cable that came with an Audio Technica ATR2100 microphone. There is
a second jacket inside the outside jacket. If the cable is the same as
the one at the link below, the inside jacket is a "Conductive PVC Shield."

https://www.bhphotovideo.com/c/produ...ies_XLR_M.html


** The Pearstone cable has a spiral, copper grounding shield - says so the "overview".

It also states the purpose of the conductive PVC shielding is to reduce electrostatic ( ie handling ) noise.


How effective is the conductive PVC shield?



** Very effective at the stated purpose.



.... Phil



And exceptionally good value, especially if those are real Switchcraft
connectors.

geoff
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Scott Dorsey Scott Dorsey is offline
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Default Conductive PVC Shield

Phil Allison wrote:
mcp6453 wrote:

** The Pearstone cable has a spiral, copper grounding shield - says so the "overview".

It also states the purpose of the conductive PVC shielding is to reduce electrostatic ( ie handling ) noise.

How effective is the conductive PVC shield?


** Very effective at the stated purpose.


Agreed. Cables that use just the conductive plastic tend not to perform that
well, because the thickness of the plastic (and therefore the resistance) is
different in different directions. There are a couple European manufacturers
making cable like this.

But cables that use conductive plastic combined with a proper shield do very
well, and the plastic almost eliminates handling noise when used for high-Z
connections.

For pro audio where everything is 600 ohms or lower, handling noise should
not be a huge deal, but it still occasionally is, and the conductive plastic
is cheap insurance. It beats graphite, which works well for reducing tribo
noise but makes a mess when you terminate the cable, and which can cause
leakage resistances if you don't clean the mess up.

I am curious though whether the PVC increases the ruggedness of the spiral
shield. I never liked spiral shields because they are much easier to damage
than braid shields, but I'd think that PVC layer might hold them in place
better.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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