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Sun Jul 13, 2008 12:56 am
PostPost subject: Cabling - Types and Run Distances Reply with quote
Bruce Wilkinson



Joined: 06 Jun 2007
Posts: 15

There are several types of cabling in an Axia system. It can be a bit confusing since good old CAT-5E or CAT-6 network cabling is used for quite a few different purposes. Our "Introduction to Livewire" found here (http://www.axiaaudio.com/manuals/files/IntroToLivewire2.1.pdf ) has some of this information, and more, on page 41

An excellent technical paper on the topic of cabling has been presented by Steve Lampen of Belden. That paper is found here: http://www.axiaaudio.com/tech/cable/Axia_Cable_Guide.pdf

This topic will attempt to provide some additional clarification.

Ethernet Network - Whether it is a Livewire network or not, there are distance restrictions on twisted pair cabling used for Ethernet. Do not attempt to exceed 100 meters (328 feet). Make sure you use CAT-5E for all 100 Mb/s runs and we recommend using CAT-6 for any 1000 Mb/s runs.

CANBus - An important thing to remember is that CANBus is a BUS. Therefore, it needs to be properly terminated at each end. Please refer to our tech note on this topic for details. The maximum total length of all CANBus cabling associated with a specific Element should never exceed 100 feet (30 m) and this includes the length of the power supply cable that connects the Element surface to the PSU unit since it is also a part of this bus. The PSU cable itself should never exceed 40 ft as noted below. Our tech note found on the Axia web site here http://www.axiaaudio.com/manuals/files/Element_Termination_10312007.pdf will provide details on CANBus termination.

Analog Audio - Network cabling makes great analog audio cable since the twists are very precise. As long as your audio is properly BALANCED, and operating at a standard line level such as +4 dB, you can run a long distance over twisted pair. A few hundred meters should be no problem. After all, this is how your voice used to travel right across the country when you used the old analog phone system.

AES Audio - Steve Lampen from Belden has presented several papers including discussions on the use of unshielded twisted-pair cable (UTP) for AES audio. In summary - it works just fine. Cable runs of exceeding 100 m are acceptable. Depending on the sample rate, you may even go longer distances.

Element Power Supply - As discussed above, this is a part of the CANBus cabling system so you should keep this length to a minimum. A practical maximum is about 40 ft. This means that the Element PSU will usually need to be located in the same room as your Element control surface. The Studio Mix Engine can be located anywhere on your network since it requires just a network connection.

Can I use CAT-5E cable for microphone signals? In a word - no. Lets think about this for a moment. Good audio cable has crosstalk and noise specs that are in the order of -90 dB at audio frequencies. When our signal is +4 dB (line level), this looks pretty good. If we look at the performance with a microphone level signal that is in the order of -50 dB as compared with +4 dB, well - things just don't look so good any more. We have just lost 54 dB of noise performance since our signal is so low. And then there is that pesky, little detail of phantom power - it needs a ground reference. Our recommendation is to use high quality shielded, twisted-pair cable for all microphone signals. This is one of the reasons our microphone nodes use standard 3-conductor XLR connectors.

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