Yeah, I looked at the manual once I got the model number. It's designed to be driven from an external speaker output - a power amp output itself - and not from a line level output even though the input is high impedance like a line input.
So it is not designed to handle a "normal" line level like the P25RX puts out. Too low.
If I could see the schematic of the unit I could probably suggest a modification that could make it work. Likely there is an audio attenuating pad in front of the first preamp input. If you could bypass that pad (just some resistors) you could probably make the unit a LOT more sensitive.
But without a schematic I can't be sure. Only other option, at this stage, is to put an actual audio line driven audio power amp between the P25RX and the NES10-2 MK4.
The device is actually designed more as a special enhanced powered speaker to overcome ambient room noise using the filter circuit inside (presumably to boost up speech range frequencies while reducing non-speech range audio frequencies especially boosting those speech components that the average human ear is less sensitive to and reduce most non-speech noise components) and not to actually drive up the whole audio level. According to the documentation, the input maximum is stated as a power level of 5 watts rms and so is the output! That is telling as is the instructions to set the level of the unit to be the same whether powered on or off - this device's primary purpose is active filtering and not level boosting.
-Mike
