This problem is hardware related and involves the preamp gain pot of this nifty little blue box which is for the rest working OK.
“OK” was mentioned here instead of “fine” because from this unit on I realized that one XMAX-branded preamp is not the same as other similar branded preamps in more expensive units. There is definetely a difference. OR.... there is a relationship with the proplem discribed below.
There is something wrong with the linearity of the preamp gain and I presume the 1-2 pots need replacement, due to a manufaturing and/or design flaw, or another modification in the preamp design (like a change of a resistor value), depending on the design with I do not know, is needed.
Within the last part of the pot dial there is a very audible and highly unusual jump in preamp gain.
Also please mention if this is only affecting certain serial no.
This problem is not unique and mentioned on the Presonus forum before.