Why my JBL GO 2 is making a hissing sound?

Hi,

Do you still get the audio signal with it or is it just the hissing sound only?

How is the audio signal connected to the speaker, BT or cable?

If via BT, try connecting an audio signal via a stereo audio cable connected to the aux input socket to check if the hissing sound is still there or not.

This is just to check if the problem is related to the BT area or the amp area of the speaker.

If it is only when using BT, try using a different BT signal source to prove whether the problem is with the speaker or the original BT source.