inspecting the pcb, I found that the 0V tracks of the voltage
stage and current stage are not connected. This
is not a fault in manufacturing.
designers prefer to have high current grounds separated from
voltage grounds to lessen the possibility of contamination.
all common grounds will be connected when the Hartke is fully
the bench, the amplifier module will not work unless the grounding
yellow wire under the pcb does exactly that. It connects the
voltage stage 0V with the current section 0V.
the module is fully functional.