Digital Mixer

Will Fraser

Digital Mixer

Today portable digital mixers are quite common. These units are popular because they need very little outboard gear having processing such as dynamics and EQ built into the mixer. Soundweb London can also act as a portable mixing device. Soundweb London can provide the user mixing capability coupled with drive rack style processing all built into one or two racks spaces. Since London is controlled via Ethernet, this also adds the capability of controlling the system via wireless connection and helps eliminate the need for extra bulky cabling and allows the user to move freely about when making adjustments to the system.

Control Panels

In this example two BLU-100’s are programmed to act as a 24x16 mixer. A control panel was created that looks like an actual mixer to make using the mixer more intuitive. The custom panel for the mixer is designed to fit on a screen with 1366x768 resolution which is a common resolution on newer laptops. The idea is get all of the common controls on the main page and make navigation easier and intuitive. This is accomplished by using control panel sub pages in London Architect.

If you look under control panel pages you will see each channel under the main mix section has its own group of child pages for the input settings, dynamics processing and equalization. The controls that need to be accessed frequently such as faders, mutes and the meter bridge are all on the Mix page making all of them visible when on the Mix panel. Controls that are not accessed often are setup on sub pages under the Mix page. This makes them visible only when that sub page is selected. This also lets you to have easy access to any of the common parameters with a simple button press. The aux sends, loudspeaker processing and control room sections are under different parent pages because they don’t share the same controls as the main mix section.

Another feature we wanted on the main control panel was to see instantly what processing was active on any of the channels at a glance. For this we simply added LEDs representing their on/off state and linked them to the bypass buttons on each of the processing blocks.

Signal Flow

Each of the BLU100’s has 12 mic/line inputs and 8 outputs. The BLU-100 utilizes the first 48 channels of the London High Speed Digital Audio Bus to get audio from one unit to another. Since our mixer is a 24 input mixer, we will need to bus the twelve inputs from DSP 2 to DSP 1. Because we are processing our aux sends in DSP 2, we will also need to send the 12 inputs from DSP1 over to DSP 2. For each input channel we have a gate followed by a compressor for our dynamics and then a parametric EQ. To balance the processing between the DSP’s we will run the signal through these processing blocks before sending them to the digital buss, this way each unit is responsible for processing its own inputs.

All the signals are then routed to an automixer. We use a gain sharing automixer with the direct outputs turned on. The direct outputs are routed to a BLU link Tx node. This allows us to bus these signals between London devices as well as throughout the design. We can route these same signals for our meter bridge, individually assignable aux outputs with metering and a true solo bus that affects only the headphone output.

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