Universal Pedal Interface – Updated 9-9-01

I have just completed the MOTM protyping work on a universal pedal interface. Why
is it called "universal?" Because it accepts just about any kind of pedal you can imagine.
As you may know, Yamaha and Roland decided to make their pot connections just
opposite on their respective control pedals. One connects the pot wiper to the tip of the
TRS plug and the other to the ring of the TRS plug. It matters not. The universal pedal
interface accepts either at the same jack. In fact, if you have an actual control voltage
pedal that does not have the range and bias control you wish it had, you can even
connect that to the universal pedal interface. Yes, it still connects to the same jack.

Here are the general specs of the MOTM prototype:

Accepts pedals with 8.5K, 50K or 100K pots (jumper selectable on board) (Yamaha FC-7 is 50K, Roland EV-5 is ~ 8.5K) Or, a simple resistor change on the board during construction can enable other pot size options. Pedal control range +/- 5.0 volts, plus bias Bias control (+/- 2.5 volts) can be used with or without pedal. Can be used to bias DC voltage (accepts real CV pedals too) Gate out – You set the threshold of what pedal position triggers the gate. Mix in - use to add your pedal voltage to some other DC voltage.

The original pedal interface was somewhat different. It was a 2-channel device without
the added GATE and MIX functions. Here is some information about the original circuit
as I proposed it to Paul.

Channel # 1 features:

Bias control pot (reversing +/- 5 volts)
Hi / Lo range switch (7.5 or 5 volts)
Dual outputs (+) and (-) active at the same time.

Channel # 2 features:

Bias control pot (reversing +/- 5 volts)
Range control reversing pot (+/- 7.5 volts)
Single output since range control is reversing.

Click here for a photo of the original prototype.

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