Yamaha DTXpress/DTXplorer/DTXtreme

A two or three zone pad has only one piezo.  The rim switch is
connected to the connector ring and is used by the module to determine
if it is the main area or rim that has been hit.  You therefor cannot
feed a piezo into the connector ring (and you risk blowing up the input).

It can be done using the "magic box" which turns two piezo signals
into one signal plus a pseudo rim signal.  (search the archives or
look for the "DTXpander cheap.pdf" circuit in the files section if you
want to build one).

Keith.