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3
AVB Networking Basics
3.3
Choosing the Right Cables
StudioLive™ Series III
AVB Networking Guide
3.3.2
Shielded vs. Unshielded
Conductor
Insulation
Pair shield
Sheath
Shielded Twisted Pair (STP)
Unshielded Twisted Pair (UTP)
Conductor
Insulation
Sheath
Conductor
Insulation
Pair shield
Cable shield
Sheath
Shielded and Foiled Twisted Pair (STP)
Foiled Unshielded Twisted Pair (UTP)
Conductor
Insulation
Sheath
Cable shield
Whether you use CAT5e or CAT6 cable, you will have the option to use Shielded
or Unshielded cable. Both cable types can be used for AVB networking and have
advantages, depending on the type of AVB installation you are designing.
Shielded twisted-pair (STP) cables provide a barrier to help interference,
especially electromagnetic interference (EMI). STP cable is constructed
with additional electrical shielding along the length of the cable as well as
specially constructed plugs that electrically connect and properly ground the
cable shielding to the device connected at each end. Originally developed
for industrial applications, shielded cable is ideal for fixed installations
where Ethernet cable must be run near power, fluorescent lighting, etc.
Like a balanced analog cable, STP cables have to be grounded, so you’ll
need to use STP-compatible RJ45 connectors. Most XLR-style locking
Ethernet connections you will find used on Pro Audio equipment, like
the StudioLive Series III mixers and NSB stage boxes, are designed to be
able to support both shielded and unshielded cable connections.
There are some specific use cases which might call for shielded Ethernet
cable to prevent electromagnetic interference (EMI) or radio-frequency
interference (RFI) from affecting the performance of the cable. It should be
noted that if shielded cable is used but not implemented correctly, it can
introduce problems and make things worse than using unshielded cable.
As with everything in audio, if you are not experienced in installation or
design, it’s well worth the investment to consult a professional who is.
There are several different acronyms commonly used to describe shielded cables
where the twisted pairs are not themselves individually shielded. These cable
types rely on an overall shield or screen to filter out external noise. While you
may find them used synonymously, there are important differences to note:
•
SF/UTP. This cable features a braided screen (S) and a foil shield (F) that
surrounds unshielded twisted pairs (UTP). Cables with an overall braided
screen are great for applications that need extra protection from EMI.
•
S/UTP. This cable features a braided screen (S)
surrounding unshielded twisted pairs (UTP).
•
F/UTP (FTP). This cable uses an overall foil shield (F) to protect
the unshielded twisted pairs (UTP) and is essentially very similar
to a simple UTP cable, offering very little protection.
