Concepts

The purpose of this article is to demonstrate how a complex audio interface can be used as a stand-alone device and essentially alleviate the necessity of a mixer. Specifically, with the proper implementation of virtual I/O routing, external enhancement processors and digital hybrids can be integrated seamlessly into a production rig. Virtual I/O Routing is performed by using a software application that offers the same capabilities as a hardware mixer. For example: dedicated inputs can be routed to any single output or group of outputs in the same manner as utilizing Auxiliary Buses on a hardware mixer.

It's important to note that capturing tracks individually will require a multi-track recording application [DAW] that is compatible with the interface of choice. This concept will provide a powerful and efficient method of customization and recording in terms of individual track access, software effects processing and mixing.

For this demonstration I decided to use familiar gear. The Motu [Mark of the Unicorn] 896 HD is a multifunctional firewire audio interface. It has been my component of choice for about two years. The Telos One Digital Hybrid is the industry standard for recording standard telephone audio at the highest available quality. The Aphex 240 is a very affordable and easy to use two channel dynamics processor [compressor/gate]. We finish our production rig with a pair of Shure SM7 B broadcast microphones.

Objective

Production requirements are as follows: the broadcast program will consist of two individual hosts. The individual host channels will require independent effects processing. External telephone audio must be introduced on an independent channel in order to address any problematic issues in terms of levels, noise, etc. The host channels need to be equally available to the caller for seamless interaction. Lastly, three independent channels will need to be incorporated into a virtual multi-track recording environment.

Hardware Implementation and Routing

Let me stress that the integrated inputs on an audio interface, or the signals routed to these specific inputs will be available within your multi-track recording application via firewire. Full customization is possible. Outputs on the audio interface can be used to feed external control-room monitors, surround sound matrixes, or in this case, inputs of external processors and/or devices.

Let us begin with the microphone channels and routing path: the microphones are connected to interface inputs one and two respectively. At this stage, both channels can be incorporated into your muti-track software application on individual channels. However we are interested in a much more complex method of integration. In order to process the mic channels before we introduce the audio into our project, we must create a bus, or proprietary routing path.

Notice that in Fig.1, interface outputs 1 and 2 feed the inputs of the Aphex effects processor. The outputs of the processor feed inputs 7 and 8 on the audio interface. To sum things up - the mic channels are sent out of the interface, through the processor and subsequently returned to inputs 7 and 8 on the interface. They will be incorporated into our multi-track project fully processed on an individual basis.

CueMix DSP

CueMix DSP is proprietary software that is bundled with all Motu audio interfaces. It runs as a stand-alone application.This is the tool that will help us with our bus configurations. Keep in mind that the configurations are retained within the interface itself. This provides stand-alone use of the interface. Alternative devices and manufactures offer similar software applications that provide the same customization features.

Processor Feed Bus

Fig.2 illustrates the Processor Feed Bus. Mic inputs 1 and 2 are sent out through the processor and returned to inputs 7 an 8 on the interface in preparation for project incorporation.

Digital Hybrid Feed Bus

In this aspect of our project we need to supply the host audio channels to the hybrid input so that the caller can hear the hosts speaking on their mics. Secondly, we need to incorporate the caller's audio into the audio interface in order to insert the channel into our multi-track project independently.

The Hybrid Feed Bus [Fig.3] is configured as follows: Mic inputs 1 and 2 are routed to output 5 on the audio interface. Keep in mind that this output selection is arbitrary. In fact, any available output can be utilized. Output 5 feeds the input of the digital hybrid. This supplies the hosts dialog to the caller.

The output from the digital hybrid feeds input 4 on the audio interface. This will supply the caller audio back to the hosts, and it will be available for multi-track incorporation independently.

Multi-track Configuration

In the final phase of our project we need to associate our source channels with specific tracks using compatible software. In this case I am using Motu's Digital Performer for demonstration purposes. ProTools, Cubase and Logic Pro are other examples.

As illustrated in Fig.4, our three source inputs are integrated into 3 individual mono tracks. [mics from interface 7 and 8, hybrid from interface 4]. Using this method, a recording session will provide each channel on an independent track prior to mixdown. All channels are routed to the Master Output channel.

Additional Notes

If you require additional software effects processing, simply insert plugins on individual tracks. You may also consider adding an additional Auxiliary track into the multi-track project. This concept can help maintain system performance and efficiency. For example: if you are working with multiple instances of a single plugin for each track, and individual parameters are not required, try inserting the plugin on the new Auxiliary track only. Route your channels to the Auxiliary track for universal processing before the signal hits the master output. In this case one instance of a plugin will help with system performance and efficiency as previously noted.

-ptfigg. ny

10.10.2006

Copyright © 2006 P.Figgiani Msc All Rights Reserved