I use one of these with my Peavey Midibase unit and this one is extra (2 can be chained for 8 note polyphony instead of just 4 note.) Can be used with any midi controller (computer, keyboard, peavey cyberbass or midibass, or other midi equipped basses.)
Here is a thread of my midibase doubling up with this particular synth unit:
Peavey Midi bass (midibase) clip
As you can hear it does a phenominal sub octave sound. And it has a selectable +/1 1 or 2 octave setting as well as all 12 notes an ocatve up (examples maj6th, 4th, 5th, minor 3rd.) In the clip I do a 6th up or something at the end.
Includes unit and power adapter. Decent looking condition. Works perfectly.
$75 plus shipping. ($15-$25 in the US)
I can get a pic if needed.
I also have a parts thread in my signature and usually have a bass or 2 up. I actually also have an extra peavey midbase for sale.
Thanks,
Joe