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Possible to make Moog EP-3 Universal Expression Pedal function with HD500?


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I own a Moog EP-3 Universal Expression Pedal which has been rather fantastic for all that it is rather big and heavy.


I cannot get it to work with my HD500.  Reversing the polarity switch does nothing.  I'm assuming that 1/4" TRS is universal (or are some 1/4" Tip+Sleeve only) and that 1/4" TRS is what the HD500 is manufactured to accept.


When plugged in and not adjusted, the Editor shows it as pegged at 100%


If I finesse the adjustment knob on the pedal to somewhere up in the last 8-10% of it's range, I can get the 'knob' in Editor to back away from Max.... and if I'm very careful, all the way to MIN.

The only problem is, once establishing min-max and confirming that communication is happening, Any movement forward on the pedal pegs the "knob" in editor to MAX and any move backwards on the pedal immediately pegs the indicator to MIN.


So, at the moment, I can configure it to be an on/off switch, or a 'choose lower value' to MAX switch... i.e., if I adjust until the indicator is at 50%, then all the way off is at 50%, and anything other than off is MAX. 


This is an excellent pedal.   What's the deal?  Impedance?


Can I build a custom adapter with resisters to attenuate signal, or a transformer to step the impedance into the correct 'range'?   What are the published specifications for the HD500 that an expression pedal needs must conform to to work?


I figured out how to calibrate the on-board pedal, but nothing for the external.  I assume no such functionality exists.



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