For yesterday's practice I left my Carvin rig at home and took my SWR Bass 350 amp with a 210 cab. I ran it at about 66% gain and 66% master volume, and I ran a line out to the PA. I got a very loud hum coming through the pa. When I run the same setup and turn the the amp up in my garage, I can hear a hum too. But it's not nearly as loud. This is the first time I have used this smaller rig so I don't have any past experience to compare the performance too. Can you guys offer me some advice on what might be producing this, and how to troubleshoot or resolve this? Thanks!