So I got my Mainline assembled last night and it passed all checks that were in the instructions, but when I turn it on there's a constant low hum on both channels. Which terminal numbers do I need to check, in particular, for any grounding issues?
Details: The hum doesn't get louder or quieter with volume changes, it's not loud at all, and it starts as soon as I flip the power switch regardless of if any inputs are connected (I haven't checked the XLR port but the 1/4" port definitely has the issue with my ZMFs plugged in). My transformer bell has continuity to the grounding lug but I'm unsure what other terminals I'd need to check for soldering issues.
Thanks!