Usually this indicates bridging the hot to ground on the input jack. It looks like there is a lot of solder on the center pin of that jack, so it could be extending across the plastic insulation. Check carefully and remove solder if possible.
You were correct Sir. One RCA jack was shorted on my crack exactly where you indicated. Now it's fixed and it sounds great. When I get a chance I will attempt a reinstall of the Speedball.
Before I move on to that however, whenever I turn the volume pot, up or down, I get a lot of these scratching sounds through my Sennheiser HD650's...
Please advise me guys. You've proven able to correctly detect the particulars which I continually neglect, and I'm moved.
It'd be nice to get one more round of your sound advice.