Are you using 1/4" jack connectors ? If so, it is possible that you are connecting an unbalance input to the balanced inputs of the H8000. This will give you low signal and a lot of noise. Sounds like you need to look at your connections.
It looks like the Minimoog probably gives out about +4dB at full shout, so this should light about the bottom 3 leds. If it does not do so, it would again indicate some kind of connection problem.
Lest you wonder, the reasons that I am so sure that the problem is at your end are as follows:
1) Our gear is pretty quiet.
2) Even if there were a hardware problem, it is unlikely to occur simultaneously in both audio boards. It could be a mysterious power supply problem, but this would probably have more dramatic symptoms.
3) If it's only lighting the bottom led on the meter, it's going to be noisy.
There is little value in discussing the nature of the noise until we are sure that you are giving the unit a good signal.