i think it might just be the New Metal Input jack i had installed the amp had a Roland plastic input jack which was stock and until i replaced it its been having so many sound issues do you think id be able to get he original input for the amp and have it installed instead because ever since i got an amp tech to put this metal input jack in the guitar its Had all this hum it never had before also when i hit the chasis it picks it up which im pretty sure never happened before with the plastic input jack its like this new metaljack is somehow picking up all this interferance maybe it wasnt installed properly i need help getting my amp back to normal anyone else know much about roland cubes what should i do this thing has so much hum now with this new jack that i cant even really turn it up loud when i play or it drives me nuts...Im about to go freak out on the dude who installed this new jack because he just diminished the sound of my amp Hardcore...this thing used to have no hum and be super clean even on High Gain and i want that back what should i do!!!! where can i get original parts for roland cube 60 amps .?

Hey this is a weird question but when you turn up my amp loud and actually hit the cabinet of the amp with no patch cables plugged into the input the speaker outputs the sounds and you can get it to have feedback or just make a thumping noise is this normal do most amps do this thanks alot for the help