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Ethernet Cables for AVB Guide

Article Published August 9, 2019

The PreSonus StudioLive Series III Ecosystem uses Audio-Video Bridging (AVB) for all of its audio networking. PreSonus implementation of AVB requires a gigabit Ethernet link. Not all Ethernet cables on the market can achieve Gigabit speed. Only Cat5e and above can consistently achieve Gigabit speeds. The length of the cable also plays an important role in speed performance. A Cat5e cable that is longer than 100 meters (328 feet) is not guaranteed to achieve Gigabit speed. If the connector on the end of the cable is poorly crimped, the cable may fail to perform as it should. It is also important that Ethernet cables maintain a snug connection with the AVB port on your PreSonus gear. If that connection is poor, then you may experience drops in audio. 

Here is a simple test to determine if your cables may not be making a good connection.

  1. Plug both ends of your Ethernet into AVB ports on devices that are powered on. 
  2. Look at the amber colored LED on your PreSonus product next to the AVB port. On the SW5E, look at the amber light on the left of the device that corresponds to the Ethernet port the cable is plugged into
  3. Gently tug on the cable in every direction.
  4. If you ever see the amber light turn off, you should not use that cable for AVB. 

Cables may pass this test and still not be perfectly suited for use with AVB. This test only checks how well the plug fits in the AVB jack. If a cable fails this test, it is definitely not a suitable cable. 

Here is a list of cables that PreSonus has tested and verified that they maintain a solid AVB connection. This list will be updated as more brands are tested. 

  • Elite Core SuperCat5e with Neutrik NE8MX6 Ethercon connectors
  • Elite Core SuperCat5e with shielded RJ-45 connectors
  • Panduit TX-6 Plus cables
    • Panduit also sells the TX-6 Plus connector. These are great for installations where cables need to be terminated on site. 
  • Quiktron 570-130 Snagless Cat5e
  • Belkin A3L791 Cat5e patch cables
  • Comtran Cat6 23 AWG patch cables
  • Whirlwind ENC6ASE Shielded Cat6a cable 

It is recommended that when not using Ethercon-style cables, you use cables with “snagless’ connectors. This means there is some form of a guard to keep the locking tab from getting caught on things and breaking off. Cable manufacturers have come up with several different solutions to make connectors “snagless”.

Ethernet_Connectors.png

PreSonus AVB products use Gigabit switches and ports. There is no reason to use a cable which is capable of 10Gb speeds (Cat6e and higher). Ethernet Cable spec also sets a length limit of 100 meters. That is 90 meters of solid-core, install-grade wire, and 10 meters of stranded patch cables on the ends. 

A Deeper Look Into Ethernet Cable Variances

Ethernet_Cable_Variances.png

*There is no TIA standard for Cat6e. It is an augmented version of the Cat6 spec.
** Some say Cat6 is capable of 10 Gb up to 55 meters.
***This table only covers Ethernet cables that are compatible with PreSonus AVB enabled products. Cat5 is not compatible.

How to interpret Ethernet cable Speed?
10 Mbps = 1.2 MB / s i.e. 1 hour to download a DVD (4.5 GB)
100 Mbps = 12 MB/s i.e.  1 hour to download 10 DVDs (assuming 4.5 GB average)
1.0 Gbps = 125 MB/s i.e. 1 hour to download 100 DVDs (assuming 4.5 GB average)
10 Gbps = 1.25 Gbps i.e. 1 hour to download 1000 DVDs (assuming 4.5 GB average)

From: https://customcable.ca/cat5-vs-cat6/

Technical Note from Official Cable Specifications from TIA. 

The Telecommunications Industry Association (TIA) is responsible for setting the standards for Ethernet cables in the USA. TIA-568.2 is the specifications that deal with copper twisted pair Ethernet cable such as Cat5, Cat6, etc. There are three revisions as of 2018 to this spec: TIA-568A, TIA568B, and TIA-568C.2. Cat5e cables on the market today may be built to any one of the three revision standards. A and B cannot be used together because they specify different colored wires to be inserted into connectors in different orders. TIA-568C.2 (the .2 just means twisted pair cable) builds on TIA-568B and adds tighter guidelines to eliminate crosstalk and electromagnetic interference. This spec is mainly used in Cat6 and higher cables. 

Technical Challenges with Ethernet Cables

Crosstalk and electromagnetic interference (EMI) are two of the challenges that can inhibit a cable from reaching its expected speed performance. As the category of twisted pair Ethernet (Cat5e, Cat6, etc) goes higher, more specifications are added to eliminate crosstalk and EMI. Also, the TIA-568C.2 specification, which covers all of the categories, adds tighter specifications to eliminate crosstalk. 

Unregulated manufacturing processes is another major issue. Ethernet testing equipment is very expensive. Fluke Industries, a company that makes these expensive testers, estimates that 80% of Cat6 cables on the market are not built to TIA spec. There is no authority that checks cables produced to ensure they actually meet the specification that is printed on the cable jacket or packaging. Also, there have been problems with some manufacturers cutting corners, literally. They trim the corners of Ethernet connectors to make them easier to remove from molds. This can obviously cause a poor connection. Some manufacturers use worn out or uncalibrated tooling. Manufacturers charge more money to replace tooling more frequently. They sometimes over-crimp cables causing a poor connection or make connectors that do not fit tightly with other brands. 

Imperfect field terminations cause connectivity issues as well. It is easy to over-crimp a cable. It is also easy to insert the wires in the wrong order. A popular RJ-45 (also called 8P8C) 4connector type allows for the wires to pass through the end of the connector. They are then trimmed with the crimp tool. Wires that are not trimmed clean and flush to the connector can cause issues. It is important to maintain the twist of the wires all the way to the connector as well. 

Not all RJ-45 connectors are designed the same. Some are specifically meant for solid core wire, some specifically for stranded wire. Using a stranded connector with solid core wire can break the solid wire causing a bad connection. Some connectors are designed to work for both solid and stranded wire. Some connectors are specifically for Cat5/Cat5e, others for Cat6 or Cat7. Some manufacturers or installers use Cat5e connectors with Cat6 cable and call it a Cat6. If you look at how the wires are laid out in a Cat5e connector, you will notice they are in a straight line. Cat6 connectors stagger the wires. The reason for this is Cat6 generally uses a thicker gauge wire: 23 gauge for Cat6, vs. 24 gauge for Cat5e. The wires have to be staggered in order to maintain the spacing needed to make good contact with the pins. 

Heat build-up can also negatively impact the performance of a cable. Heat can be from equipment the cable is connected to, from POE (Power Over Ethernet), or just the temperature of the environment it is in. Some companies account for heat build-up in order to guarantee that a cable will be able to hit the expected speed at 100 meters. If you need to make a Cat5e cable run of more than 50 meters, it’s possible that heat could keep it from achieving 1 Gigabit speed. 

Shielded vs Non-shielded

From: https://www.mouser.com/pdfdocs/alphawire-Understanding-Shielded-Cable.pdf

“There are two types of shielding typically used for cables: foil and braid.
Foil shielding used a thin layer of aluminum, typically attached to a carrier such as polyester to
add strength and ruggedness. It provides 100% coverage of the conductors it surrounds, which is good. It is thin, which makes it harder to work with, especially when applying a connector.
Usually, rather than attempting to ground the entire shield, the drain wire is used to terminate
and ground the shield.
A braid is a woven mesh of bare or tinned copper wires. The braid provides a low-resistance path to ground and is much easier to termination by crimping or soldering when attaching a connector. But braided shields do not provide 100% coverage. They allow small gaps in coverage. Depending on the tightness of the weave, braids typically provide between 70% and 95% coverage. When the cable is stationary, 70% is usually sufficient. In fact, you won’t see an increase in shielding effectiveness with higher percentages of coverage. Because copper has higher conductivity than aluminum and the braid has more bulk for conducting noise, the braid is more effective as a shield. But it adds size and cost to the cable.”

Some cables use a combination of foil and braid surrounding all the pairs. Some add shielding to the individual pairs as well as a shield around all the pairs. Cat6a, Cat7, and Cat8 cables should all be shielded. In order to achieve the maximum data rate, crosstalk between wires and EMI must be kept at a minimum. Cat6 and higher cables use a spline (plastic cross-shaped divider) to separate the pairs to cut down on crosstalk. They also utilize thicker outer sheathing to cut down on Near End Crosstalk (NEXT) and Alien Crosstalk (AXT). 

If you use shielded wire you should also use shielded RJ-45 connectors. Shielded cables should have a drain wire that can be terminated to the shielded RJ-45 instead of terminating the wire shielding to the shielded connector.  

All PreSonus AVB products have been electrically tested with non-shielded cables. There is no significant need to use shielded cables with PreSonus products unless you are in an area with significant EMI such as an industrial plant.

 

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