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AES Section Meeting Reports

Pacific Northwest - June 1, 2013

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Summary

For June 2013, the PNW Section held an all-day workshop on CAT-type cabling for portable audio. Organized by PNW Committeeperson Dan Mortensen of Dansound, Inc. after some personal experiences with such cabling, several experts spoke and demonstrated, and attendees had the chance to try creative abuse to several types of cable and look for failures. 26 attended (13 were AES members), including AES Executive Director Bob Moses. The meeting was also webcast (a simple webcam and room mic) for anyone unable to physically attend.

This was the PNW Section Business Meeting, so its election ballot was presented. With a quorum present and no motions for write-in candidates, Chair Dave Tosti-Lane asked for a show of hands to accept the ballot by acclamation.

As is our custom, PNW Chair Dave Tosti-Lane had everyone briefly introduce themselves. Dan Mortensen introduced the day's activities and what led to this meeting. Dan recently encountered a problem on the job, with a continuous white noise sound emitting from the FOH system when he was positioning his CAT 5 cable transporting digital audio packets between the snake head and console. The positioning involved pulling on the cable while it was somewhat constrained by other, large cables causing both a stretching and pinching of the cable. The noise went away when he stopped pulling. This aroused his curiosity.

Steve Lampen of Belden presented a detailed history of "CAT" cabling and Ethernet, along with many obscure facts and details of cable construction.

Next, Dan showed photos of the different twist rates of different pairs in several brands of cable. Steve noted this was all "secret sauce" by manufacturers to meet the stated "CAT" specs. Steve also showed an example of an interesting "instant snake" adapter for use with CAT 5/6 cable (ETS InstaSnake), and he showed Belden single pair CAT 5 cable, which his bosses thought was a dumb idea, but is a big seller.

Kurt Denke is the owner of Blue Jeans Cable in Seattle, and a vendor of assembled AV cables for home and industry. Blue Jeans is a Belden customer and can actually sell "made in USA" network cable assemblies, although he also sells some import AV cables. He demonstrated and spoke about cable termination and RJ-45 connectors, and performance testing. Steve noted that Belden has the patent on bonded pairs in CAT cable, and he'll send you a Belden pair splitter gizmo if you email him.

Mac Perkins (Pacific Studios) joined in and the three discussed terminology of CAT cable, such as permanent links, patch and channel cables, and how testers treat each differently. Field-installed RJ-45s usually won't meet CAT 6 specs, said Mac. Kurt continued with info on the $9k Fluke Networks cable testers, its adapters and testing criteria for different cable types.

A lunch break was held, with attendees free to find their own lunch and bring it back for socializing. After lunch, some door prizes were awarded:

Continuing after lunch, Mac Perkins spoke and demonstrated CAT cable testing instruments. He described TDR (Time Domain Reflectometry), a time-tested technology where a test signal is applied to a cable and precise measuring shows locations where impedance changes and discontinuities occur in a cable, and showed his vintage CRT Tektronix 1502 TDR tester. Also shown were several Fluke Networks testers (about $9k), and less expensive testers from Fluke Networks ($400) and Greenlee ($200). The high-end Fluke unit performs quickly, automatically and does extensive cable tests which can fully certify a cable to industry specs. Apparently, a simple continuity tester is considered next to useless!

Steve Macatee (Rane) joined in the discussion, with comments about Ethernet, latency and transport timing with audio data protocols like SuperMAC, AES50, Dante and AVB.

Lastly, for the rest of the afternoon, some space was cleared so that attendees could physically abuse many types of cables while connected to digital mixers and digital audio snakes, looking for data interruptions. Abuses included extreme pulling, yanking, rubbing with live power cables, stomping on, and even driving a 2 ton stage scissor lift repeatedly over a cable. This torture testing did lead to some discoveries that were not always as expected. Some extreme forms of abuse did not induce data disruptions, and some cable construction did prove to be better against abuse.

For an extended report with moderator Dan Mortensen's detailed conclusions, go to the meeting archive at the PNW Section website, http://www.aes.org/sections/pnw/pnwrecaps/2013/jun_cat5

Special thanks to presenters Steve Lampen (Belden), Kurt Denke (Blue Jeans Cable), Mac Perkins (Pacific Studio), Rick Rodriguez (Fluke), who provided a handout of the essentials of CAT cabling for digital audio, and Cornish College of the Arts for making the Raisbeck Performance Hall on the Cornish campus available for this event.

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AES - Audio Engineering Society