Zoom's PodTrak P8 is a great, feature-rich audio interface for use with Ecamm Live. It can add some powerful features to your broadcast such as the ability to use the P8's sound effects pads and other features.
Fixing Doubled Audio
However, some configurations may result in a doubled or echo effect in your broadcast for sound from sources other than your microphone. If you encounter doubled audio, activate USB Mix Minus. To find this setting, tap the USB icon on the PodTrak's on-screen settings, and then activate the USB Mix Minus toggle.
Once you have followed these steps, PodTrak will no longer be looping the Mac's output audio back into the input.
Other Reasons for Echo
If you're still hearing an echo in your broadcast, you may need to activate Ecamm Live's Echo Cancellation.
If you're hearing feedback of your own voice coming from your speakers, ensure that you don't have Ecamm's Audio Monitor feature turned on.