On my setup, the MP-201 in unipolar mode doesn’t quite reach the full range of [at least] the cutoff knob on the 101. (nor does an expression pedal for that matter) But that’s easily remedied by trimming up cutoff until the lowest frequencies are audible; at that point, you’ll be able to reach the far end of the pot. On mine (again, these things are calibrated at the factory so your mileage may vary) that’s just north of 9 o’clock on Cutoff when playing a ‘middle C’ on Phatty’s calibration tone.
Bi-polar mode from the MP-201 does some strange things, there is an audible low pitch tone (that doesn’t match what I’m playing, in other words, it’s a droning low frequency, not anything tied to resonance) with the heel at 0. At a certain point you’ll get beyond this as you step towards towards toe (on mine, the 0..4095 value was at 1700) then the normal range will begin. This would have me think that you can go a bit further on unipolar mode but there is no way to adjust the bottom, therefore it’s not very usable and there is a pop or some scratchy sound between the drone sound I mentioned and filter fully engaged even when changing the heel value.
On most if not all of the Foogers, the knob is additive (or an ‘offset’) to whatever the pedal is sending (and it doesn’t matter which pedal) so you can get a bigger range (where a pedal might normal reach about 180 degrees of a knob turn) by trimming up as I mentioned above. I haven’t tried all of the inputs but the 105’s Envelope certainly behaves this way.
And certainly, from a voltage perspective, the MP-201 goes 0-4.96 on my multimeter and a -4.something up to the same value in bi-polar.
One often misunderstood aspect of expression pedals in general. The ‘device’ whether it be a Voyager, Phatty, or MoogerFooger, sends 5V on it’s Ring (the middle conductor of a TRS or Stereo jack). The EP-2 and most expression pedals are passive, so they can only take the incoming voltage and return some reduced value.
The MP-201, on the other hand is an active voltage device and actually SENDS it’s own voltage, though within range of the 5V which Moog products expect and are compatible with. It’s therefore also useful on Modular gear which typically does not provide a supply voltage.
I should also mention that I have recently acquired a ribbon controller which was custom built to supply voltage above 5V (it has a 12V power supply and a built in actuator. I keep it at a safe value (upwards of 7v) and can tell you that the Moog equipment (Voyager Old School in this case) certainly reacts favorably to it (ie. I get more range). But you should exercise caution when playing with Voltage, especially if you plan on getting into the use of MULTs (combining CV on VX-351s or CP-251.
At least that is what I found… hope this helps somewhat.