Excessive Feedback!!

I am using a DigiTech RP-155 which has it's own ASIO driver. I recently purchased a 3 channel mixer. I downloaded ASIO4ALL and it recognized the mixers driver, which is USB Codec. Okay...I also recently put TH-2 into my Reaper. As soon as I arm my track...I get a large amount of feedback. Only when I turn off the armed button does it stop. All of my drivers are up to date...I have tried numerous combinations via the system sound settings...Reaper's audio settings...changed input/outputs etc... I could really use some help on this one. Thanks in advance!!

You're connecting an output to an input somewhere, creating an instant feedback loop. Check all your connections.

I looked up the RP-155 and it's a guitar pedal and I know TH-2 is an overloud amp sim and you didn't say which mixer you are using...you should also give more details because I'm confused what you are trying to do.

It's an ART Project Series USB 3 Channel Mixer. I would really like to by pass my Digitech, and use only my Mixer, and the TH-2 from time to time. When I've tried to do that, nothing works. Sometimes I just want to use my DigiTech, which I generally have no problems with. I want to be able to have the ability/flexibility to be able to use both devices without issue. Are they competing against each other? Thanks again!!

Somehow the output coming from Reaper is routed back to the armed input. Most probably it's a routing error you made on the ART mixer, but no way for us to tell you without knowing your complete routing setup.

Would you be able to give me what you think would be the best way to route assuming you the the devices? Thanks!!