I've got a Groove Tubes Brick, and I'm not getting a high enough level out of it. I'm using a balanced XLR->TRS cable, and I think the input may be set to unbalanced, I have the gain on the tube all the way up, and it barely tips the meters in the red when I am right up on the mic. I've tried both condensors and dynamics, as well as instruments.. with the same results. I think that the brick might be bad, but I'd like to ensure that its set for the correct operating level before I call groove tubes.