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SX20 Grounding Issue

We are having a grounding issue with our SX20. Currently we are using a ground lift plug and that is working at the moment. This issue is a buzz/humming nice. We have swapped every piece of equipment out and still have the issue. Ground in the confrence room itself has been checked.

The only thing i can think of is a compatablity issue.

The system was orginally a C60 Dual Profile 52

We swapped out the C60 and installed the SX20.

For about a month everything was fine then we started to hear this noise. Again when we use the ground block we no long hear the noise.

What do you think.



Re:SX20 Grounding Issue

Hi Kristi,

Would be able to confirm two things.

Do you find any difference when not connecting the presentaion cable to a pc or laptop with audio connected.

Are you taking out the audio via Dnam or external speakers.

Most common reason for the humming buzz is speaker wire.
Make sure no on changed the input and output ports for audio at the back of the codec.
Have u connected two monitors on both the hdmi out or just one.

Ravi kr.

Sent from Cisco Technical Support Android App


SX20 Grounding Issue

Hi Kristi,

are you saying that you have replaced C60 codec wiht SX20 in Profile C60 unit ?

SX20 is a quickset codec and it not a intergrator like C60 codec. moreover, profile units has a DNAM ( Digital Natural Audio Module) which is responsible for Sound output.

In case of SX20 codecs, it is necessary to use ground loop isolators with active speakers.

Cisco Employee

SX20 Grounding Issue

Hi Kristi,

Attaching a grounded active speaker system will create a ground loop. This causes an annoying humming sound.

Solution 1:

SX20 and C20 should be used with non-grounded active speakers.

Solution 2

: Buy a ground isolator and connect the audio cable through the isolator. Example:

How to create a cable

breaking the ground loop when the speaker system has balanced input:


Kind regards,


Cisco Employee

SX20 Grounding Issue

Hi Kristi,

You can also try using Ground isolator (Carpower by Monacor FGA-40) and use it with the SX20 Device, hopefully this would resolve the Buzz/humming Sound.