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Biamp Systems

VTC with Cisco TelePresence Codecs

This article describes the basic physical connections required for interfacing with a Cisco TelePresence product. This article also includes disabling the AEC (Acoustic Echo Cancellation) or Echo Control and Loopback features in the Cisco codec.

This is not meant to be an exhaustive product guide to the C40; some settings and interface screenshots in the Cisco software may change as their user interface is updated. Some settings are similar in the C60, C90, and other Cisco products.

The SX10 and SX20 are reported to be recommended for use as standalone products and not used as an integration product. The SX80 is a common source of frustration as settings are made via CLI (command line interface). Please contact Cisco for support if needed. Verify that the far end is handling echo cancellation for you. If they are routing your audio back through their codec you will hear an echo which will stop when you mute the input from the SX80.   

Physical connections

C40 IO.jpg

Biamp to Cisco

An output on the Biamp device will be connected to the C40's Mic/Line In (balanced XLR) connection. This will carry the audio being transmitted (VTC Tx) to the VTC far end.

  • The Cisco's Input type should be set to Line.
    • Phantom power must be turned off for the C40 Mic/Line Input (defaults to off in Line mode)
    • The Cisco's input level should be set to 0 (defaults to 0 in Line mode)

balanced Phoenix to balanced xlr.PNG


Cisco C40 input.jpg

Cisco to Biamp

The C40's Line Out (unbalanced RCA) connection will connect to an input of the Biamp device. This input will be the audio received (VTC Rx) from the far end which will play out in the room.

  • AEC, if available, must be disabled for this input channel on the Biamp (AEC is only for microphones).
  • Phantom power must be disabled for this input channel on the Biamp.
  • In the Cisco device, ensure that the Audio > General > SelectedOutputConnector is set to Speakers.

Unbalanced out to balanced in.PNG

Cisco C40 output.jpg

See the Cisco C40 physical interface guide document for further detail.

AEC / echo control

AEC can only be provided by one device in a system, in this case we are using the Biamp device. Each of the mics must be connected to an AEC input with AEC enabled.

The C40's Line Out must be connected to a Biamp input with AEC disabled, or to a non-AEC input.

The EchoControl mode (acoustic echo cancellation) must be turned Off within the C40 interface. Please see the Cisco documentation for further details -


Within Cisco video codec

There are settings in the Cisco video codec which will route the Mic/Line In back to the Line Out and give a direct echo. This can be easily recognized as it will be a clear echo with a slight delay. If you mute the video codec input to the Biamp the echo will go away. If you experience this with the Cisco C40, look in the C40's Audio > General Settings and ensure the SelectedOutputConnector is set to "Speakers".

Via Crestron DM

If you have a second output from the codec into another mix device the echo issues may originate there. This is often a source of frustration with the SX-80. The analog path to Tesira is the expected one, but there is also audio on the VTC’s HDMI connection to the Crestron DM. Be sure to mute the audio in the Crestron DM for the VTC’s HDMI input.
If you hear the echo, as a test you can mute the program input from the Crestron DM and leave the video codec active and the echo should go away. If this stops the echo you will need to examine your routing in the Crestron DM.
If left unmuted you will hear direct echo at the far end (VTC Rx > HDMI > DM > Pgm In > VTC Tx) and/or garbled audio since the mics will be getting routed back to their own AEC Ref (Mics in > VTC Tx > VTC > HDMI > DM > Pgm In > AEC Ref)
VTC secondary audio path via DM.png
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