Hi guys, newbie here. I have a GK 800RB head and a Yorkville Y210B 2x10 8 ohms cab. I'm running a cable from the low 300watts 4 ohms into the cab. Now, my understanding is that I shouldn't have the Bi-Amp button pushed since I'm not using two cabs. However, with the Bi-Amp button NOT pushed, I can hear a loud annoying hiss along with the sound of the bass (the bass sounds great, but with lots of hiss). If I push the button and turn it into Bi-Amp, there's no hiss anymore, but the bass doesn't sound the same anymore... It sounds muffled. I know I'm not supposed to use the Bi-amp option but that's the only way to get rid of the hiss. But why the bass sound gets muffled? Am I doing something wrong here or is just the amp that needs repair? Thanks!