I just got the hd300 and I love it. I'm running it into the effects retur. Of my peavey Valveking.  Unfortunatly I'm having a volume issue. I have both the channel, master, and back knob button turned all the way up, yet it's barley loud enough for practice, let alone shows. Is there something wrong with this unit? I'm using the preamp models, set to stack power amp, and the back is set to line, amp, and ground. Any help would be great, thanks!