Yamaha DTXpress/DTXplorer/DTXtreme

Thanks for the reply & suggestions, Chris.

> And you've checked the manual, making sure there's no global or 
master audio output gain settings for the module that need to be 
raised (aside from the sldiers)?

I did now.  It's in the UTIL menu, master volume, already set to 127, 
which is its max.

> As far as the clicking, that sounds alot like something called 
a "MIDI Ground Loop".   Do a search on Yahoo!, and you should get 
some info on what it is, and how to address it...

I couldn't find abything about this, but it sure sounds interesting.  
Speaking to the tech, he mentioned that all MIDI boxes have an opto-
isolator between the MIDI and audio circuits, and that he checked for 
any DC connectivitiy.  Still, since he was unable to re-create the 
problem (and didn't even agree the output level was low, which it 
most definitely is), so I'm really not so sure about this guy.
 
> But a simpler first step to run out induced noise would be to make 
sure you're running different cable types separately, NOT parallel to 
each other (if they must cross, run them at right angles).  

I'll do that right now...

Just audio to powered speakers and keyboard to MIDI in, no wires 
crossed or even close to each other until they get to the DTX.  Same 
problems.  Level too low, so speakers all the way up, turn DTX either 
off or on, play keys and hear faint little clicks coming out of the 
tweeters.