Just got a Maxon OD-9, but can't use it because I get a fuckton of feedback when it's on. I use it with a Jackson RR1 with EMG's and a Marshall JCM2000.
I tried it with a JCM900 and it worked a bit better, but still not good.
Could it be something in the wiring of the EMG's? It was the previous owner who put them in. Or do I simply have a faulty pedal?
Post settings. Most people use a tubescreamer with only a small amount of gain, and the level/output CRANKED. Try it that way, if you're not already.