Hey TB, I've started noticing this lately...it's like a "farting" noise, I guess a bit like a blown speaker sound -- but I'm pretty positive it's not my cab. I'm running my Hondo P-bass into a Hartke HA3500 with a Hartke 410XL cab. I set the tube preamp to "4" (11 o'clock), the solid state to "1" (7 o'clock), and the volume is usually at 1 or 2 when just practicing. I say "lately" because I've started messing around with pick style and I only get this noise when I dig in near the pickup. If I compensate by playing near the bridge it only occasionally happens, but right above the pickup it's a mess. Achtane, why don't you just lower your pickup height? Well, here is the weird part -- if I turn up the solid state and turn off the tube, I can beat the crap out of the strings and don't get this sound. It's only when I turn up the tube at all. The amp was made in 1999, and from the seller, "I changed the tube to a JJ ECC83S two years ago." Aside from playing more softly, is there something stupidly simple I can do or should I go ahead and order a new tube? The amp is otherwise in mint condition. It's not a huge deal, but it is annoying.