Has anyone ever had this problem with the DSL 401,or know what could cause it? It has a low volume high pitched noise that is there constantly,as it warms up it gets more pronounced! It has been there since i had it shipped to me,I bought it used,and i replaced it with new preamp tubes. They were all 12ax7 but they had different letters after them,the guy at store said it was allright. Any help appreceiated! You can e-mail me too.Thanks

dtm16@peoplepc.com