Since I started kava 2.5 years ago I have had this. It doesn't bother me,though, it's not like other types of tinnitus, this one seems benign. It's a low level buzzing and it is always there, but not irritating or unpleasant, and I almost always simply ignore it. Like a soft warm fuzzy buzz, like the sound of flannel.
But if it's irritating, like yours is, you want to take that seriously. Obviously the first test is to stop kava and see if it goes away. Then re introduce and gradually titrated upwards doses so you can locate the specific point, quantity of kava, which triggers the effect. It might be that any quantity produces it, in which case you might have to make a tough choice. Maybe try candies or extracts, see if you get the effect?