Will:

I know you are obviously hearing hum from something. If it were as loud as you say in my 950, I would have no problem hearing it from my horns. Have you compared the hum _relative to_ the level of music on the blue dot 950 verses the old one? This would at least establish if the hum is higher by the increase in gain of the blue dot. Is the hum louder, less loud, or about equal to the level of the hiss, at "0" and "+10"? This will give a rough indication on the level of the hum. Is the hum only audible at "+10"? If so, how loud is music when you play it at that volume? How loud is the 950's internal test tone when the volume is at "+10" (after you have done a normal calibration at "00")? If you give me this last info, I can set my 950 to the the same level of the test tone with an SPL meter and see how audible any hiss/hum is.