I have a Thunderbird Pro IV active bass, love the sound and everything but unless you roll completely back the high frequency knob there is a very audible buzz, when i up the volume on my amp the same noise becomes audible again, which means it's always there but at low volumes the eq makes it imperceptible. I have some experience with electronics and have tried to diagnose it myself but so far i haven't been able to pinpoint the cause, is this a usual problem with active instruments? Has anyone found this kind of problems before? Some notes on what i've already checked based on other threads and forums: - Already switched both cables and amps so the problem must be on the bass itself. - Originally the bass also had ground noise, i made it go away by connecting the bridge to ground as it was ungrounded. This noise seemed out of place to me as the pickups are humbuckers but this solved that problem. - I've already checked the soldering and grounding on every component, everything seems in order, nothing is loose nor rusty. - Another thread recommended wiring the positive pickup wire to the battery but this made no difference. By default i believe this connection is not made as the eq is active but the pickups are passive. - When using a (very) short cable the buzz is reduced greatly, this has lead me to believe it might be picking up radio frequencies or something like that. When connected to my full pedalboard or a long cable the noise becomes louder. - Another for the radio frequencies: once had a gig near a radio tower and the bass picked up a lot of radio noise, ground lifting de DI didn't help at all. Ended up having to play with a passive bass. I'll really appreciate any ideas or suggestions! I really like the tone of the bass and i would hate to end up selling it because of this problem. Thanks in advance.