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Post by Animalbeats » Mon Mar 22, 2021 12:18 pm

Can someone explain how the EP-3 works...

Is the BK-100k72

a Log or Linear pot?

Does it have an altered taper?

There are 2 100K pots, but is says 50K resistance, is this the equal divide of the 100k pot?

What is the second "scalable output knob" pot for exactly and how does it work?

Help is appreciated.


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Re: EP-3

Post by Markyboard » Wed Mar 24, 2021 12:01 pm

Hi -

Not sure where you got your info from. Anyway this (left pic) looks reasonable although I cant confirm the accuracy:


It is how most expression pedals with a polarity switch and range knob are configured .

The range knob sets the minimum value of the expression input. With foot pedal in heel-floor position you can set it to give some intermediate value instead of 0

Both pots are linear. Logarithmic (or alter tapered) pots are typically used for volume pedals

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Re: EP-3

Post by Vinny999 » Thu Feb 02, 2023 12:15 pm

That diagram looks reasonable, but also wondering the same thing and what is the correct info. expressionpedals.com lists the Moog EP-3 as a log taper 100k expression pedal (they also list EP-2 as a 50k linear taper). I measured the resistance on the pedal I just received and it comes to around 85 kOhm ring-to-tip and 85 kOhm ring-to-sleeve in heel position, and 45 kOhm sleeve-to-ring and 200 Ohm ring-to-tip in toe position (Standard polarity, trim knob fully clockwise). It is hard for me to tell the taper by measurement, but seems pretty even as I move treadle. With the trim knob at vertical, I measure 110-35 kOhm ring-to-tip when moving the treadle heel to toe, and 85-45 kOhm sleeve-to-ring, which might suggest a nearly linear taper. Can someone confirm the specs? These are unusual characteristics for an expression pedal, as the responder says; 100k log would be more typical of a volume or wah pedal. Thanks.

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