Building Your Own SAC System (August 2010) By Bob Lentini www.softwareaudioconsole.com Building your own SAC system can be an exciting and amazing adventure. SAC systems can be created in all shapes and sizes and can be built for incredibly low cost. Of course, if budget allows, your SAC system can be the most expensive console ever constructed, the choice is yours. The systems are extremely scalable and can be any number of input and output channels up to 72 at the time of this writing. If you are not comfortable working with computers at the component level or are not skilled with your hands at assembling things, you may want to consider purchasing a turnkey system from one of the turnkey system integrators that are listed in the Links option on the website. This document will give you an example of assembling a SAC system from start to finish. Remember, there are unlimited variations in choices of hardware and assembly methods and this example is just one method that creates a very stable and high performance system. You may find some of the concepts and techniques presented in this document useful in your own SAC system construction journey. Let's get started. One of the first things I like to do at the start is to gather some of the basic elements I will be using during the various construction phases. An assortment of screws, tie wraps and clamps of various kinds can all play an important role in constructing a clean and solid system that can be transported to and from events without breaking down.
I also find it very handy to have some sort of labeling machine that easily labels cables with a wire wrap format as well as a banner type format that can be used on flat surfaces for labeling channel numbers and other connection references. The machine I use is called the IDPal from Brady. While this particular model is no longer being manufactured, there are many current choices that replace it. Choosing Your Components You must first decide on the components you will use, such as sound cards, mic pres, analog to digital converters, the type of computer case, the overall rack case, etc. The system I am building here is a 48 channel system. I chose to use two of the RME HDSP Digi9652 sound cards which are 24 channels of ADAT optical i/o each. Selecting the sound cards first allows you to see what kind of slot configuration your computer motherboard will require, as well as the i/o configuration needed to interface with the converters. These cards use PCI slots and after some exploring, I selected the ASUS P5Q Pro Turbo motherboard which has the necessary two PCI slots as part of its layout. This motherboard supports the Intel E8500 Core 2 Duo CPU, which was readily available at a reasonable cost, as well as a high speed ram option. I selected Windows XP Professional as my OS, and decided to use 4 gigs of 1200 speed ram, which forced the motherboard to overclock slightly to 3.6 ghz. While there are a variety of front-end choices using high priced mic pres coupled into high priced converters that could raise the price of your system into the tens of thousands of dollars, I decided to use the Behringer ADA8000 mic pre / converters, since they offer an amazing value at an extremely low price point. These units offer 8 channels of mic pres and line inputs as well as 8 channels of balanced line outputs, plus AtoD and DtoA converters all in a single 1U rackspace box. It requires 6 boxes to handle the 48 channel system design. I first chose an XFX ATI Radeon 5450 video card, but this card caused extreme buffer slipping when redrawing the display. I then switched to an older Diamond ATI Radeon 4550 HD video card and all buffer slipping issues disappeared.
A lesson to be learned here is that certain components can interact with motherboard chipsets and other components and cause difficulties. Keep an open mind when exploring different component options if the system exhibits problems. I decided to go with a custom built rack case on wheels, made of 1/2 in birch wood laminated with a durable rubberized surface and configured as a shock mounted design. I like wood cases, instead of fiber or plastic cases, because I find it easier to screw clamps and cable mounts inside to facilitate a neat and clean finished product. Assembling the Computer I chose a 3U computer rack case that is only about 15 inches deep. You can find a variety of these shallow depth cases in 3U and 4U styles on the web. I used a SATA boot drive mounted in a removable bay so swapping a system imaged drive is fast and simple in case my Windows install ever gets corrupted. You can see in this image, that I used 4 chassis cooling fans, two in front and two smaller ones in back. This allows the system to run 24/7 without temperature issues. I generally like to add a second physical drive for all data. This allows my boot drive to remain at a small (100 gb) size, so drive imaging is easy to maintain, and can be restored quickly without concern for overwriting and loosing data. This image shows the basic computer build before the sound cards are installed. I like to get Windows and all basic components installed and tweaked before moving on to the sound card drivers.
This close-up of the CPU shows that I like to use one of the bolt-down CPU fan assemblies, rather than the typical plastic push-lock default fan units. The push-lock units can easily pop off when the system is jolted during transport and the boltdown units will take a lot more abuse. There are many models of these bolt-down fan assemblies from different manufacturers which can be easily found on the web. This image shows the finished computer with the RME sound cards installed. When using multiple sound cards to attain your desired channel count, be certain that the sound cards you select allow multiples on a single driver. Also, pay attention to clocking issues. The cards and driver must be able to allow proper slaving and sync to one master clock source. These RME cards allow me to set the first as the master clock and then connect an internal sync cable between cards and tell the driver to sync the second card to the first. I will set the ADA units to sync to the incoming ADAT optical pipe clock.
Assembling The Rack There are various options to address all the cable connection issues a system of this size needs to handle. Generally, using 1U back plates with 8 male and 8 female xlr plugs per converter, connected with short jumper cables and mounted on the rear rack rails creates a neat and clean setup, Or, multi pin snake connectors can be used along with custom made back plates for a quick connect setup. Unfortunately, both of these options can add serious cost to the system. In this case, since the Behringer units have the mic inputs mounted in the front, and xlr outputs mounted in the rear, I chose to use inexpensive short 8 channel jumper snakes to keep the front of the system neat and extend all input connections to the rear of the rack on the floor. By keeping all wiring in the rear of the rack tied off to the sides, the xlr output plugs could easily be reached directly, eliminating the need for extenders of any kind for the outputs. Even though the snakes were color coded, I used my label machine to neatly wire wrap channel numbers on each cable connector to give me a clear reading on the front of the system of which channel is which.
Laying the rack on its back can make the mounting of the gear much easier to handle. I used a Furman power conditioner mounted at the top of the rack as my master AC control and also to simplify AC cable installation. I then began mounting the Behringer units one by one with a small half rack space between them. This space is used for two things. First, it allows air flow between units, which can be very important, because these units tend to run hot. Second, it gives me the opening I need to weave the small snake extenders between units and keep the input connections clean, neat and manageable. When mounting the units in this manner, I use the bottom two screws for each unit, because it holds the units more securely since gravity forces the tops of the units tightly against the rails even without the top screws. This image shows the procedure I followed as I continued mounting the units into place.
Each snake is neatly positioned tight against the previous unit and the next unit is mounted, holding that snake in place. This image shows all units in place, with the addition of a Behringer HA4700 4 station headphone amplifier. Next I mounted the computer case in the bottom of the rack.
And here is a look at the front of the finished assembly. Next, I moved on to the rear assembly and the task of connecting everything together. This can be a daunting task as the amount of cables and connections can quickly grow into a tangled mess if you do not pay close attention to detail as you go.
I started with the AC cables, neatly tying and clamping them to the rack case and directing them over to the left side where most of the AC connections were found. I continued along, labeling, and tying off each AC cable for each piece of gear. I tucked the bulk of the cable mass into the small space between the rack case and the units themselves to keep them out of the way and make room for what was still to come. I also mounted a separate power strip, switched from the Furman, to handle extra power needs.
Next, I began securing the snakes to the rack case and neatly arranging them along the right side. Keeping the snakes tied to the right side kept all the output plugs open and easily reachable. Clamping the snakes in this manner also takes all the strain from the front connectors and allows me to easily manipulate them behind the system.
Next, labeling the outputs makes for a clear visual of which output is which. I then cable tied the snakes together in groups, making it easier to find the correct channels when making final connections to large snake tails or stage connection boxes.
Next, the optical connections were dealt with. I chose to use a flexible optical cable from Oculus. These cables are encased in rubber and are much more manageable than the typical plastic optical cables, and the cost was not much higher. Since these do not come cut to length, I used the left side of the rack case to clamp and loop them to take up the slack. Remember, you do not want to crimp these cables, they must remain smoothly coiled. I then routed the optical cables neatly along the rack bottom and into position snapping them into the sound card connectors. These cables snapped in fairly tight, but it is still generally a good idea to carefully use a small amount of clear rubber silicon to lock them securely in place.
The final touches on the system added a rack mount fan assembly to keep a constant flow of air thru the Behringer units. And there we have it. Our very own SAC system, complete with 1920 x 1080 monitor, mouse, keyboard and 1 Behringer BCF2000 fader pack. Who would have ever thought that you could build your very own Midas, Yamaha, Digico, Venue, or whatever your favorite console used to be, in your own garage. And what's more, you have not only replaced 1 of those expensive consoles, but you now have FOH and 24 more monitor consoles. Welcome to the SAC Experience... there isn't anything quite like it. Have fun creating your own SAC System!