I have a gk backline 600 I started to go over some songs when I started playing it sounded like my speakers were blown I thought it might have been my battery in my pick ups were going dead I changed it and it sounded the same I changed speaker cable un plugged my pre-amp went strait to the head same thing I took to my freinds plugged it into one of his cabinets same thing so I know it’s not my basses it’s not the speakers it’s the head making it sound like that if anyone has had this experience or knows what it could be I would appreciate it