read the manual! clearly states that extreme settings of the gain or eq, coupled with high volume settings will result in microphonics/feedback/unwanted noise. yes, mesa/boogie preamps do have a limit to their settings. try swapping the v1 out to see if the tube is more prone to noise than others, otherwise, tame your eq settings. the eq in that amp is extremely reactive, and unlike a marshall where you can just leave everything a 10, mesa's have 'sweet' spots. check the manual for where these are for your amp.