I recently bought a used MXR MX81 bass preamp. I bought it mainly to use as a DI, although I now plan to use it for some tone shaping, too- if I can overcome the hiss problem with the low-Z output. The DI is hissy. It doesn't matter where the ground lift is set (and that switch's phantom power function does work), or where any of the controls are set- including whether the pedal is on or off. I get a little hiss out of the hi-z output, but the low-z is much more noticeable. I found the hiss on stage subbing the MXR in for a SansAmp that was there. The latter is dead quiet, so it's not a cable issue. It held true at home into my mixer (trying multiple cables), as well. The internal switches (DIRECT OUT and BUFFER) are both on (factory defaults). Has anyone else run into this? Thanks!