I've heard that the tube in the preamp of the Hartke 3500 is prone to noise and pops, and I think this is happening with mine. anybody know how to get to the tube to change it? should I just take it somewhere to have it done? if anybody has done this themselves please anwser back as you are exactly who I want to hear from...but anybody else is welcome to reply. any tube recommendations are welcome too. If possible please descrie the sound of the tube. Keep in mind that I do not have much money so $60 12ax7's are out of the question. I would like to be able to get a slight amount of overdrive out of the tube, but I realize that with the way the Hartke works this may actually not be possible. I know I ask a lot, so I appreciate all responses. thanks.