My Boss DR-110, a probe, and oscilloscope software - Visual Analyser 2011. You can short the different individual oscillators to ground, and they'll come out th

My Boss DR-110, a probe, and oscilloscope software - Visual Analyser 2011. You can short the different individual oscillators to ground, and they'll come out the audio & headphone jack. There's a great breakdown of how the circuitry works at http://www.sdiy.org/richardc64/new_drums/dr110/dr110a1.html http://www.sdiy.org/richardc64/new_drums/dr110/dr110a1.html - but some of the frequency values there (related to the cymbals) didn't sound right to me - though it's possible I misinterpreted what's going on at that page.