I just tested on my Rev2 keyboard to see whether that setting (Full LPF or Half LPF) changes the cutoff when a pedal is not connected... it doesn't seem to make any difference when you don't have a pedal connected... that would potentially be a bug if it was the case, but I was unable to reproduce it. When you tested it, did you power on with a foot pedal attached, and then remove the pedal after power was on?
As far as I can tell, this is not a bug... operating as expected.
I did some investigation and reflection. Follow me, if you will:
1) The previous setting issue was persistent (i.e. almost 1.5 years of regular use).
2) The cutoff knob behavior was clear, i.e. I hadn't heard the 12 dB filter close all the way until this discovery.
3) When I tried to reproduce the issue (as per Creative Spiral), it was not persistent in the same way. That being said, when I unplugged the pedal while powered on, I encountered a situation where the cutoff knob didn't work at all and the filter stayed 100% open. This persisted across power up/down and the only way to make it go away is by changing Global settings to something other than the LPF Full or Half settings and power cycling.
Given anecdotal evidence re: filter tone and bleed through complaints, I still could not shake the suspicion that I'm not the only one to experience this issue.
...So, I tried to imagine what could possibly cause the Synth to
think that there was a pedal plugged in. It occurred to me to check the difference in behavior with balanced TRS vs unbalanced TS cables. To experiment I plugged in an unbalanced TS 1/4 cable, set the global to LPF Half,
and voila! If I unplugged the TS cable the setting persisted exactly as before with the cutoff falling at just below 200 Hz. This is reproducible and persists across power cycles. I can't even get it to go away until I plug in a pedal on a TRS cable, set Global 24 to LPF Full, and the pedal to reset the range.
To reproduce/test:
1. Power on.
2. Create a default Basic Program.
3. Change Global 24 to LPF Half
4. Plug and unplug TS 1/4" cable in Pedal/CV jack.
5. Test frequency range of filter cutoff. [I get just below 200 Hz]
6. Power cycle and test knob on other settings.
I can reproduce this every time. The key is the TS 1/4" cable or...a balanced TRS that is either not plugged in all the way or slowly unplugged. This last bit leads me to go out on a limb with a big guess.
Hypothesis:All REV2s were duly tested and shipped. The global was set to LPF Half on all or some units(?). During the testing on some REV2s either the expression pedal was not plugged in all the way or it was slowly unplugged in a manner that caused this error. This would be fairly easy to overlook even with diligent testing, and since (as above) it persists across power cycles it would seem to be a "feature." It would not be readily noticeable quickly checking most presets. This could plausible produce a situation in which some units shipped with this limited bandwidth in place and others shipped working normally.
The result: wildly varied opinions on the tone of the synth and the reports of bleed through. I think we may have solved a mystery. What say you ladies and gentlemen of the jury?