Hi Cuki,
I don't know the capacitance or the impedance of the sensor. I'm assuming its output needs to mate with a high-impedance input which is taken care of within the endpin preamp.
As you can see from the photo, the sensor housing is a rectangular brass tube into which the lead wire goes at one end. Note the two dots on the surface of the tube that mates with the top of the three-footed HFN base. Are these two small metallic-colored dots the piezo elements for the system? Hard to believe that they may be! Maybe the piezo sensor is actually a longer element and the two visible dots are for maintaining its location within the tube?
I've also shown the bottom of the HFN base to show the air pocket my sanding of the base revealed. I'm not a fan of how the 3-D printing renders air pockets in the base as I'd prefer the base to be solid and free of air pockets. Do these air pockets affect the vibrational transfer from the bridgeplate to the piezo sensors? Maybe and maybe not. The sensor tube could be adhered to a modified 5-string banjo bridge which in effect would harken back to the wooden HFN base days of the original HFN pickup.
I haven't tried the sensor in a guitar but may do so by first trying it with a supplied 3M foam strip under the line of the saddle. The Schatten Artist Plus 2 system is neat in that a second pickup source can be soldered to Channel 2 in the endpin/preamp/jack and the volume of both sensors can be controlled by the dual-volume-control soundhole module. The system can be powered by an onboard 9-volt battery or by 48-volt phantom power. This makes it a system I want to play around with some more in the future!
