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 bolt-

down 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!