Alright, I'm sort of weirded out by my latest discovery of additional feedback coming from my setup.

I got a new vader cab, and I added it to my rig, and now theres around twice as much feedback as before. My noise suppressor doesn't even get rid of it all any more. But it's weird because I always thought cabs couldn't really add to feedback. I literally haven't changed anything except my cab.

My setup (is ****ty)
Peavey Valveking Head
Boss Noise Suppressor
4x12 Vader Cab
Gib SG Special

I've switched out the noise suppressor for another of the same, didn't get rid of feedback, switched out for another guitar of the same and didn't get rid of feedback. I'm sort of wondering if its the head, but it would be odd for it to act up the same day I hooked it up to my vader cab.

Any help, ideas, or .02 cents would be greatly appreciated.
Thanks Guys.
Maybe it's a grounding problem, I can't really see you getting feedback with that setup. But i know nothing on electronics. Although the Boss pedal is quite ****ty. Invest in a ISP Decimator, it's pretty much the standard for noise gates around here.
What kind of feedback is it? If it's a buzz or a hum type noise, that could come from fluorescent lights, computers, and other small appliances and electronics nearby (I can hear my Mom's coffee grinder through my amp). It could also be a grounding problem as mentioned before.

If it's microphonic (i.e., high-pitched squeal), it's most likely from your pickups.
It's a high pitched squeal, and I'm sure my pickups are part of the cause, but the only reason I'm confused, is because when I had my other cab (a valveking cab) it didn't have nearly as much feedback.