The simple days of PA systems
Radial's JS2 2-channel mic splitter
A Radial V12 custom 64-channel modular splitter
The OX8 solution
Easy and fast — Euro screw terminal connectors
Inside an OX8 with optional Jensen transformers

OX8™ Development

It used to be so simple. You connected a microphone to a PA system, turned up the volume and you were set! A PA system meant that you could turn up the voice to reach a bigger audience. As venues got larger, the PA system also increased in size. Eventually, the sound technician moved from behind the stage to the middle of the room as a means to tame the beast. All the while, stage levels got louder, drummers got bigger kits, guitarists began using Marshall stacks. This necessitated a form of playback system on stage that began with simple side fill speakers and evolved into multiple wedge monitors.

"Now if only I could hear my voice above the guitars" uttered the lead singer while the bass player exclaimed "I can't hear the kick drum!" All of a sudden a different mix was needed on stage—the monitor mix. This would be different from the main house mix for the audience: it would address the needs of the musicians so that they could hear themselves and perform comfortably. The stage tech replied: "To make this work, you need to split the mic signal to drive two mixing consoles at the same time."... and soon thereafter, the mic splitter was born.

What is a mic splitter?

A mic splitter's task is to take the mic signal and split it to various destinations such as the FOH or house mix position, the monitor desk and often, to a separate recording console.

Most professional touring companies are equipped with a large multi-channel splitter snake that will bridge the stage microphones with the FOH mixing console and the monitor desk. These are usually transformer isolated with ground lift switches to eliminate the hum and buzz caused by ground loops. Ground loops often occur when two mixers are connected together. Transformers allow the signal to pass while blocking stray DC currents. Lifting the ground disconnects the audio ground, allowing each mixer to enjoy an earth ground without interaction.

The same care and attention is needed when another mixer is required. This is most often found in the form of a recording system or on-air broadcast feed. With the recent advent of affordable digital recording equipment, the demand has steadily increased for higher quality interfaces to deliver a noise-free recording of a live performance. This has been amplified with the proliferation of live podcasts and real time broadcasting. This means that today, mic splitters are no longer solely used in big concerts, venues of all sizes are now realizing the need.

Laying out the basic design

When recording, one of the most demanding 'links' in the audio chain is the microphone splitter. Unfortunately, off-the-shelf options have always been limited by quality, noise and inadequate connectivity, while custom offerings have generally been too expensive to consider for the smaller productions.

Drawing from 15 years of expertise in building splitters and snakes of all types, the Radial design team put their heads together to create a simple 8-channel solution. It would need to be easy to use, expandable, reasonably priced and provide the sound engineer with the quality that Radial is famous for. We started with the concept that it had to adapt to all types of applications. By making it a standard 19" device, it could easily be mounted in a case or become a permanent rack fixture. Then it had to be portable for field recording. This meant that it had to be small. With 8 inputs and 24 outputs, using XLRs on all connectors would have made it huge! We decided to follow the lead set by Tascam and employ a 25-pin D-sub architecture. This way, we could reduce the size to a single rack space and still provide the needed connectivity. With everyone including Digidesign and Yamaha also using D-subs, we felt that using an accepted standard would be easiest.

We then thought about the contractor who may want to use the OX8 for an installation. These folks need a simple solution that can be terminated on site. For this, we added Euroblock (Phoenix style) screw down connectors. These are readily available at all electronic supply shops and are a very common connector for the electrical trade. This would also allow non-audio people to connect wires such as electricians or security installers to use it. With the D-Subs and Euroblock connections taking up most of the back panel, this left the front panel clear to assign for other uses. Here, we chose to add XLR inputs for quick connectivity, ground lift switches and input pads. This would enable someone to assemble a flight case with D-sub connections between the OX8 and a digital recorder while exposing the front panel to connect the mics.

The simplicity of a passive design

The OX8's audio circuit follows the time-proven success of our Radial snake systems: it is passive. Now you may ask why passive? The simple answer comes down to control... or more precisely 'who' or 'what' is in control of both the level and the audio quality.

Consider this: If the mic splitter is active, it in other words amplifies the signal. It therefore will replace the mic preamp of your mixing console. This poses a question regarding the quality of the preamp being used... are you sure you want to replace the mic preamp in your $100,000 mixer with one built into a snake? How much are you willing to pay for this second preamp?

What about control? In a live stage environment, where you may have 3 mixing consoles connected at the same time, who should be in charge of the trim control that sets the level coming from the mics? In an active system (and digital system for that matter), you only get one control point for setting the trim while in a passive design, because the microphone feeds each console on its own, you can adjust the input level as needed without interacting with the others. That's the beauty of a transformer. Each engineer can adjust the mic sensitivity to suit. Just imagine if the front of house mixer was in charge of the trim and decided to increase the gain on the lead vocal while the monitor engineer already had the volume up to maximum in the in-ear monitors. Who will lose their job when the lead singer's ears are accidently blown out?

The Radial OX8 is passive. Simple – no headaches – literally! Transformer isolation also eliminates buzz & hum caused by ground loops. This means you can be up and running quicker. And in pro touring, getting set up quickly without noise is critical.