This is one strange rack unit from the dark days of MIDI. I believe that the PTX8 was released in the late 80's but it is amazingly hard to find information on it. The one I owned came with no manual which caused me a lot of grief until I came to grips with the somewhat odd menu layout. My guess is that the folks involved with the ill-fated TX81W sampler had a go at this system's menu setup. Don't let this mislead you though, the PTX8 is a very cool drum synth capable of unique timbres while giving you the option to 'pound in' your sequences at the same time. The core of the PTX8 is a modified version of the RX5 engine. You get about 4 octaves of pitch-shift on the 32 built in waveforms which at the 12 bit or resolution gives some juicy alias noise at lower settings and mechanical clicks and clanks at higher settings. This unit has a cool setup of attacks and sustaining sections. The sustain is loopable which allows you to generate all manner of hums and whines. You can set the sustain time as well as a pitch envelope for each sound. Of all the drum modules I have ever used, this one generated some of the most unique and useable sounds for industrial. Forget about it if you want realistic drum sounds but as long as you don't mind the 8 note polyphony and you get it cheap, this is one desirable machine.
As far as using this as a drum brain with piezo triggers it works fine. It is quite editable as far as sensitivity goes and in most cases it is pretty quick to get things going (i.e. plug in a trigger and away you go). I did not notice any major timing lags and found you could pretty much use anything that makes noise to be a trigger. I had it wired up to a dummy that I hit with a baseball bat for a while and it worked pretty well (except I kept busting the piezos).
The operating system sucks pretty much, especially if you do not have a manual. I figured it out after a bit but not without a good share of cursing. It can be very confusing as to the exact chain of events necessary to save a patch for instance and it is easy to lose your work if you are not careful. Be patient though and you will figure it out.
Overall, this unit is pretty cool. It is pretty large (2 or three rack spaces) and built like brick shithouse (i.e. it would probably survive a head on collision with a Mack truck). Mine is gone and although I miss it, I sampled the hell out of it before kissing it goodbye. If you have access to one for cheap (or can rent one) I suggest you do the same as has a very cool sound indeed.