AngrySystems’
Audio’s “StudioHub+” approach.
A Technical Explanation of the Radio
CAT-5 wiring for analog and digital signals in broadcast applications:
Overview
The StudioHub+ product makes extensive use of shielded twisted pair (STP) CAT-5 compliant cablethroughout its design and implementation. In conjunction with companion termination and active amplifiercomponents (used where needed to condition the audio), these integrated StudioHub products provide aconvenient and technically sound method to wire and intermix analog and digital signals in a broadcast
facility.
STP cable, widely used in the computer industry, was selected for this new cross-platform application due
to its characteristic:•••••

110-ohm impedance and low capacitance range
excellent performance at audio frequencies
wide bandwidth for data transmission
low cost and wide availability
wide range of connector and cable management systems

CAT-5 for digital audio data transmission
A 1997 report, entitled “Review of Cables for AES/EBU Digital Audio Signals” conducted by the BBC
Research and Development Department, concluded that CAT-5 shielded twisted audio pair cable “offered
the highest performance of all the cables tested here.”1 Their tests included coaxial cables and specialcables specifically designed for digital audio, but they preferred CAT-5 cables for their overall flexibility
and applicability in mixed data applications and consistent performance.
Category 5 cables perform well for digital audio applications because they are engineered to havecharacteristic impedance of 110 ohms, and more importantly, extremely low capacitance (in the 12 pF/ftrange). This yields the fastest transmission speeds and lowest signal reflection resulting in the best highfrequency response and lowest error rates.
CAT-5 cables are engineered for data rates up to 100 Mb/sec (100 baseT networks). Since AES/EBU
signals have a bandwidth of about 3 Mb/sec (depending on sample rate), they operate well within thecables’ guaranteed performance parameters, with dependable error-free transmission at lengths up to 920
meters (over ½ mile).

CAT –5 cable for analog signal transmission
In a recent article, Steve Lampen, a senior audio video specialist for Beldin Wire & Cable writes, “Digitalaudio cables make the absolute best analog cables. You can go farther with flatter frequency response thanwith any cable designed for analog”.2 This is because due to it’s characteristic low capacitance, data cableis designed to transmit data at high velocity and wide bandwidths. At audio frequencies, thesecharacteristics will yield exceptionally flat frequency response, even over very long cable lengths.
Shielded twisted pair cable is specified for use in the StudioHub+ product to negate the effects of RFI in highRF environments and to avoid any possible crosstalk between cables in multi-cable bundles. While there isa potential for signal cross coupling between pairs in the same cable, the use of good modern design
electronically balanced circuits (especially at the terminating end) reduces this interference to negligible
AngrySystems
Audio have measured maximum crosstalk at –102dB, 20-20 kHz,levels. Tests conducted by Radiomeasured along a 200’ length of CAT-5 cable, into a balanced termination with a CMRR of 85 dB. An“average” quality balanced circuit with 50 dB of CMRR yeilded –90db with the same test parameters.3Finally, the use of a digital capable cable is recommended for facilities even where no digital audio circuits
are currently contemplated due to the low cost and ease of future digital conversion. In addition, byadopting the uniform use of a “multi-platform” cable, facility planning is simplified because any building
cable may be readily employed at any time for analog, digital or data (LAN) applications.
Other CAT-5 cable features as utilized by the StudioHub+ System
Standard CAT-5 cable features four tightly twisted pairs (8 wires total); two of which are utilized forbalanced left and right audio by the StudioHub wiring architecture.
Two of the unused wires, plus a third ground wire are employed for the “DC power link system”
which conducts +/- 15 volts through the cabling to remotely power various system auxiliary amplifiers andaccessories. These “spoke “ products include miniature matching and pre-amplifiers to conveniently
convert source equipment with consumer style unbalanced and low-level audio inputs and outputs to the
pro standards required for use with the StudioHub+ product. The “power link” approach provides phantom
style powering of remote devises, eliminating the clutter and noise associated with multiple AC power
supplies and “wall-wart” solutions.
Future applications for the additional pairs made available via the use of CAT-5 cabling will include theintroduction of RS-485 serial control signaling for “smart” spoke devises such as routing switchers andintercom signaling systems.
1– Tests conducted by D. G. Kirby, BBC Research and Development Department, and published in a paper titled“Twisted-pair cables for AES/EBU Digital Audio Signals” presented at the 1994 AES International convention,Amsterdam.

2- published in Radio World Magazine’s “Wired for Sound” section, Feb 15 1999

3– Tests set up utilized a carefully constructed differentially balanced driver and receiver on two different and adjacentcable pairs. Receivers were adjusted to provide precisely 85 and 50 dB CMRR. All measurements made with Audio
Precision “System One” analyzer.

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