I'm looking for a new set of tubes for my Ampeg SVT 3 PRO. Right now it has the factory tubes and it's three different brand of tube, groove tube, electro, and sovtek. It's been eight years since I pulled it out of the box new. The heads not as loud as it used to be and it's a bit distorted. I have heard stories about the bias voltage drifting on these things. I just ordered a set of JJ Gold Pins but after looking at a few different sites I see they don't have the highest reviews. So I'm thinking of myabe shelving them for another time and order another set of tubes. Does anyone have anything good to contribute in favor of JJ's or are they really that bad? Who has suggestions on a nice smooth sound out of one of these heads.