Content provided by: Geoff W8GNM
Depending on how you have your FLEX-6000 connected to external speakers or other audio processing hardware, there is always the possibility of creating "ground loops" that can result in RFI issues by common-mode RFI.
The way to resolve this type of issue is by using an audio isolation transformer to break the ground loop but still provide circuit continuity.
Here are several audio isolators that you can use. The range in price, the more expensive ones having a wider frequency range response, low phase shift between channels, and lower THD (total harmonic distortion) to lesser expensive devices that are still well suited for use with the FLEX-6000.
Recommended: Kript HiFi Ground Loop Isolator
Jensen CI-2RR (high end)