Yamaha DTXpress/DTXplorer/DTXtreme

The short answer is .. no.
Inputs 1-8 are STEREO inputs rather than DUAL inputs. These work only 
on stereo pads. 9-10 is meant for a dual zone pad (two piezo 
triggers), or with a y-cable, two single-zone pads. The stereo pads 
use a different technology for the second (rim) trigger. 
For a complete explanation, go to:
 
http://www.edrumweb.com/Articles/dual-triggers.html

This should answer all your questions.
I tried a switch with a y-cable and a single-zone pad. I could get
the choke function with the switch, but not a second voice. You may
be able to figure it out, but I think the switch trigger needs to work
in conjunction with a piezo to trigger. It may even be more than just 
a simple switch(resistor controlled?) 
But why not just use the rim function with stereo pads and get the 
extra sounds that way?
I'm afraid your dream of 18 pads requires a second unit!
Good Luck....Scott

--- In DTXpress@y..., brown684@e... wrote:
> I know this question has been asked a lot, but I'm still not clear. 
 
> I know you can add a "Y" cable to channel 9/10 but on 1-8 I read 
> where these are stereo inputs and don't act like channel 9/10.  Can 
> you add a "Y" cable to these channels and be able to pull two pads 
> off of them.  If you could just imagine 18 pads!!!