Tel: 905–690–4709 dk@tfwm.com - Darryl Kirkland, Publisher

Adding Fiber to Your Audio Diet

Is it time for your church to add fiber to its system?

I have had the distinct pleasure of being involved with the installation of two very large audio systems for two very large churches in the recent past.

Church “A” was engineered and specified (by others) using the tried and true method of routing signals. Very large bundles of copper, routed through very large conduits. Extensive patch bays, with complicated splitting schemes utilizing a combination of active and passive components, were installed in some very impressive looking equipment racks. More large bundles of copper were routed though more large conduits to the monitor mix position and the broadcast video studio. Great pains were taken to ensure that no ground loops were created in either the audio pathways or the AC mains power. Microphone runs of over two-hundred feet were required. Analog mixing consoles were chosen as part of the packages. The reason for these choices were many, but a large part of the decision making process was driven by the perception that digital technology is still relatively untested, and is an expensive alternative to copper wire and transformers. Installation of this system took about four weeks.

Church “B” was engineered and specified using digital transmission of audio and a digital mixing console. We used a fiber optic snake from Light Viper, with one direct, and two isolated splits (more on this later). Two pairs of fiber carried sixty-four channels of microphone sends and sixteen returns all split three ways. The console output was taken directly out in AES/EBU digital format, and sent to the power amplifiers, which were capable of inputting AES/EBU digital audio. All processing was done in the amplifiers and in the console. The standard, stringent, audio power requirement was still adhered to (your audio is only as good as your power), but the confidence level that hums, ground loops, and cold solder joints were not a problem was high. Installation time, three days.

I will leave it to your experience to guide you here. How much does multi-pair copper snake cost per foot these days, $3.50/ft.? How much do REAL transformers cost? How much is that electrician going to charge you to trench and install a couple of 4” conduits, a couple of 2” conduits, and a couple of 1” conduits? How much money does a REAL patch bay cost (including the 18 hours of termination required by a qualified technician)? How much troubleshooting time should you allow in your budget for cold solder joints and other bad connections?

Church “A” reasoned that digital technology is still relatively new and untested, and that the price point was beyond their reach. The bang-for-the-buck was just not there in their minds. That assumption was incorrect. By making the decisions that they did, they deprived themselves of some of the best audio technology available today, in addition to spending lots more than they had to.

Five or more years ago, all digital signal transmission in live audio was used only where the environment demanded it. Prices were high, and indeed, reliance on this technology was not for the faint of heart. Companies like Opticore, Otari, Roland, and Light Viper are currently producing equipment that is more robust and more affordable than in the past. Let’s go into more depth on one of the most cost-effective products available, the Light Viper from Fiberplex.

Light Viper is a division of a company that makes tactical fiber optic solutions for the military. The basic setup consists of one or more stage box(s), one or more mix position breakout boxes, some pre-made breakout cables, and the fiber optic cable itself. The stage box (called a VIS1832) comes in a couple of flavors, depending on the number of optical splits that you require, and the type of fiber optic connector that you want. The mix position breakout box (called a VIM1832) can input and output analog audio, as well as AES/EBU digital audio. Both boxes are rack mountable.

The Light Viper system utilizes a version of the clock that is used by its military cousins to sync digital audio at either 48 kHz or 96 kHz. It will accept input from an external clock, but the internal clock is rock solid. For you techies out there, the analog to digital conversion uses Burr Brown devices (that is a good thing). Using high quality mic preamplifiers is important, because the snake is your microphone preamplifier. In my experience, this is an advantage in most situations. Line level inputs to the console lowers your noise on the input side, and, with very few exceptions, the mic preamplifiers in the Light Viper are going to be better than your existing preamps. There are three-position pads on each input channel of the snake, giving you tremendous headroom and adaptability to virtually any mic or line level source. Phantom power is available in banks of eight.

Installing a Light Viper is refreshingly easy. There is no software interface. No soldering required. Simply mount the mix position breakout box in a rack space at the mix position, mount the stage box at a convenient location on the platform, or put it in the amplifier rack (remembering that power will be required at both locations). Take the pre-terminated fiber optic cable that you pulled through a 1/4” conduit in 10 minutes and plug in both ends. Take the pre-made fanouts from the DB-25 (Tascam style) connectors on the mix position breakout box and connect them between your console and the box. Plug in a microphone. You are done. To make matters even easier, Light Viper is working with several digital console manufacturers to include a direct interface.

I have seen these snakes go into high school auditoriums, 700 seat churches, and 10,000 seat churches. The sound quality would be enough to justify the installations. The freedom from noise, the ability to retrofit and expand facilities using existing conduit, the ease of installation, and the reliability all point to digital snakes as the way to go. So, once again, let’s compare that to copper. Digital- what goes in comes out. Even at distances over a mile, the input trace is virtually the same as the output trace. Try that with even 200 feet of copper wire. Now split it three ways. Get the picture? See the light!

Powered by