I have noticed this on both a Hartke Bass Attack DI, which I returned, and the SansAmp Programmable Bass Driver DI I own now. I am able to get a great fat, deep sound with the SansAmp, but when I try to dial in a more trebble sound, using a combination of Presence and Treble, I get lots of hiss. I can back down on either the Presence or the Treble to reduce the hiss, but then I don't the brightness I want. Neither one is turned all the way up. I am playing fairly new DR Black Beauties on an Ibanez SR 485 bass. Batteries are new, and I've had the bass checked out and is fine. I get the hiss through a Peavey TKO 115, as well as a Gallien-Krueger 700 RB II through a Peavey 8x10. Everything is super quiet without the Treble/Presence combination. The hiss is independent of the gain on the SansAmp- it occurs as soon as I plug in the SansAmp, and gets louder if I engage the 1/4" out boost. Any ideas on how to get a quieter background? Currently I have to turn off that channel between songs. Thanks for any help anyone can provide. edit: Incidently, my cables are new, high-quality bass cables: one Monster Bass cable, and one Planet Waves Uni-directional Bass cable. No problem there.