I run from my bass into a Electro Harmonix Black Finger compression into a SansAmp bass DI and to my amp. When I first set this up and turned on I got a horrendous high pitched continuous squeel that was really loud, I instantly tried to fiddle with different settings on the sansamp and then I gave up because the noise was destroying my brain! The other day I decided to try and have another go, after taking my BF out of the effects run for a while. Same noise again, this time I quickly turned the post gain on the Black finger right down and it dissappered. Ive now got a good tone so im not too fussed about pissin about with it but I have no idea why this was happening. I play a gibson thunderbird which I know has very high output pickups, as high and even higher than some active, but dont know if it is this or something else? any ideas?