…. I don't have a microphone
…. I only have Apple earpods

Do I need any more equipment to make jammr work, please?

Hi lorne,
The computer's built-in microphone is used by default when there is no external microphone plugged in. Is it possible that jammr is playing audio through your speakers instead of your AirPods? That would explain the feedback.

Please check that the output device in jammr's sound settings (jammr | Preferences) is set to your AirPods.

If you still experience feedback, try disabling “Play back my audio” in jammr's sound settings.

Please let me know if this does not solve the issue!