I've tried many quantisers over the years and it's the lil bit loosey-goosey, but still awesome A-156 that always tickled my fancy. The trigger in/out is essential and the guy just works without crazy menu diving or reading manuals. The scale limitations may be too limited for some but I find with a transposition input, the quantizer is a perfect fit for any mood I'd like to set within this tt stuff we'd likely be doing with a quantiser anyways.
One thing that always bothered me was that 1) I have to suck up an offset voltage from somewhere in order to set the transposition (and correspondingly, the mode) and 2) there is plenty of blank panel space to put it. So I put a normalled transposition control right on the front panel!
A 27k resistor, 10kB pot, and a new hole, and you're done. If you want more range, decrease the value of the 27k resistor. I know what range I like so this works for me I chose a range just slightly higher than 1 octave at 14st. This allows me to get decent settability with the control but still be able to get my m2 an octave away if need be. If you start setting the range really large (several octaves), a single turn pot gets really, really touchy.
The 27k is connected to the OB 5V regulator to have some isolation from the rail voltages. Since it's transpose and this is already quantised, very roughly, the error here isn't too much a concern.
The wiper of the pot is connected to the already hangin' free switch pin of the transpose jack.
Make sure you set the jumper to the upper-most position to have the same transpose and scales applied to both sections of the 156.