Are you using this pre live? You should not have uncontrolled feedback, pretty much ever, in a recording environment. If this is happening to you you may require headphones so you do not have to track while listening to monitors :)

edit: the pix is kinda over the top, it isn't required viewing to understand this concern ;)

Microphones and monitors in the same room during tracking shouldn't be necessary. Even if you don't get feedback there will be some amount of ringing added to the track which IMHO is worse than room modes. Track with headphones to avoid this as Space suggested.

The input and output controls on the ART MP pre may be a little deceptive. They do not indicate the volume of the input and output. The "input" is how hard you are driving the tube. The "output" is the volume compensation. Higher input gain means less noise and more harmonic distortion

So to get a clean sound, the input would be low, and the output would be high. To get a thick saturated sound the input would be high, and the output lower.

thank you gecko, i understand the Art tube a little better, i appreciate the feedback, lowell? funny im in lawrence

This pre sounds like fun. I like playing with sound, I want one.