The Alesis DM5 is an
entry-level electronic percussion module. It can be triggered by any
Midi instrument, or by a set of
electronic drums or triggers hooked into any of its 12 trigger inputs. In this last case, a nice
A-D converter converts the trigger signal to a Midi note with
velocity information and plays the sample associated with that note.
The DM5 can store up to 20 unique drum sets, which I have found to be more than enough. Some of the predefined sets are nicer than others, but it's a remarkably easy-to-use unit, so redefining sets is not hard.
It makes a good drum module for an entry-level drummer, but it lacks both an effects proccessor and any way to add new samples, so it is limited. Sample editing is limited to volume, stereo pan, and 7 steps of pitch.
A nice feature it does have, though, is something called "Expanded Dynamic Articulation" - hitting a drum sample harder doesn't just increase the volume, it (in some cases) changes the character of a sample slightly to reflect the higher velocity. So if you hit a snare drum sample (for example) harder, you'll hear the ringy overtones often associated with that drum.
The DM5 has a decent selection of samples - just over 500, with about 100 kick drum and 100 snare drum samples making up the bulk of that. If you can afford it, a DMPro or Roland TD-8 are nicer "brains", but for the musician who needs high-quality samples and who does not have huge amounts of cash on hand, the DM5 offers pretty good reponse and nice sound selection.