Yamaha DTXpress/DTXplorer/DTXtreme

I think that it is only a problem of midi notes. The pad must send the right
midi note to the redrum. You should find the midi notes used by the redrum
and then configure your kit(in the voice menu) with the right midi notes. If
you don't know which the right notes are, just hit a pad and change the midi
note each time, then write down the midi notes which work and configure your
kit.