Yamaha DTXpress/DTXplorer/DTXtreme

Gee,
I would have thought the answer would be:
- cd goes to mix-in channel.  that channel has its own volume control on it. 
In addition,
your cd player has a volume control.
- there's a master volume on the DTX that controls the drums and the cd 
volume.

Between the cd volume, the mix in volume, and the master volume, you should 
be able
to get the mixed volume where you want it.  I can on my dtexpress I.

I do have to tweak the cd volume (ususally turn it pretty high) and turn up 
the mix in volume,
and turn down the master volume to get the right mix.  But at least I didn't 
have to buy
an external mixer.

Cheers,
Andy