Room Combine – Automatic Mic Mixers

Multiple Automatic Microphone Mixers (AMM) can be linked to function as a single AMM. This can be done when an AMM is needed with more than 32 inputs, or more commonly it can be used to allow AMMs in a room combine scenario to function independently when the rooms are divided, or function together when the rooms are combined.

Basic AMM Linking
To link multiple AMMs, you first need to place one of the AMMs in Master mode and all the others in Slave mode. This is done by opening the control panels for the AMMs and selecting the appropriate mode for each AMM. This will cause additional inputs and outputs to appear on each AMM, along with an “S” or “M” indicator in the bottom right corner of each AMM to indicate the mode.

When an AMM is operating in Standard mode, each channel is compared to the average signal of all channels to determine how much gain should be applied to the channel. When an AMM has been placed in Slave mode, each channel is instead compared to a control signal received on the Sum input. This Sum signal is the average signal level of all channels from all linked AMMs and is created by the Master AMM. This signal needs to be routed from the Master AMM to each Slave AMM. This can be done using standard wiring or using Audio Routes. If the AMMs are in different devices, these signals can be routed over Dante.

To create the Sum output, the Master AMM needs to know the average signal level of the channels in each of the Slave AMMs. The Chain output from each Slave AMM is a control signal representing the average signal level of all channels in that AMM. This signal also includes the Chain input signal. Using the Chain inputs and outputs, it is possible to wire from the first Slave AMM, through any other Slave AMMs, to the Master AMM. As with the Sum signal, this can be done using standard wiring or using Audio Routes. If the AMMs are in different devices, these signals can be routed over Dante.

With the Chain and Sum signals connected, each AMM will be able to determine the appropriate gain for each of its channels based on the levels of all other channels in all the AMMs. However, the Mix output from each AMM will still be only the microphone signals from that AMM. The Mix output signal also contains the Mix input signal, so the Mix inputs and outputs can be used just like the Chain inputs and outputs to aggregate the signals from all the Slave AMMs to the Master AMM.

The Mix output of Slave AMM 1 contains only the microphone signals from AMM 1. The Mix output from Slave AMM 2 contains the microphone signals from AMM 2, plus the AMM 1 microphone signals from the Mix input. The mix output of Master AMM 3 contains the microphone signals from AMM 3 plus the AMM 1 and AMM 2 microphone signals from the Mix input.

AMM Linking with CRRs
When combining rooms with Conference Room Routers, the AMMs need to function independently when the rooms are divided, and function as a single AMM when the rooms are combined. To accomplish this, all AMMs need to be placed in Slave mode. The Chain output is the control signal that represents the average signal level of all channels in the AMM, and the Sum input is the signal the AMM compares to each channel to determine the amount of gain to be applied to each channel. The Chain output of each AMM needs to be connected to the AMM Chain input on the CRR and the AMM Sum output of the CRR needs to be connected to the Sum input of the AMM.