What does the Xpression fX Black Magic Motion control system, do?
It works in the same way as an expression pedal. When connected to the expression jack of a guitar effects processor or keyboard, it will provide remote control over a parameter chosen for modulation such as Wah-Wah or volume. The amount of modulation is directly related to the amount of movement the sensor makes when it is attached to a moving object, such as an arm.

When connected to a MIDI controller it changes MIDI controller codes between 0 – 127. The amount of change is directly related to the amount of movement the sensor makes when it is attached to a moving object, such as a leg.

When connected to a MIDI receive port on a 3rd party unit such as a keyboard, it passes continuous controller (CC) messages. The CC messages can then be routed within the 3rd party unit to control effect parameters.

What is the difference between the TRS and MIDI models?
The TRS model connects to a foot controller socket and modulates assignable effect parameters via voltage control. The MIDI model connects to a 5 pin DIN MIDI receive socket and modulates assignable effect parameters via Continuous Controller (CC) messages.


Which model do I need?
Some 3rd party units have both MIDI sockets and TRS sockets. However, some 3rd party devices have only MIDI sockets or only TRS sockets. Also, even though a 3rd party device may include a MIDI interface, this does not guarantee that the 3rd party device will provide suitable functionality.

For example –

  • Yamaha® Motif XS6 has both MIDI sockets and foot controller sockets and allows assignment to many varied parameters. So in this instance either model is suitable
  • The Line 6® POD2 has MIDI sockets but does not have a foot controller socket and so only the MIDI model would suit.
  • The Zoom® G3 has a foot controller socket only, and does not include a MIDI interface and so only the TRS model is suitable.
  • The Casio® CTK-551 keyboard has a MIDI interface, however the keyboard only allows for Xpression fX control over the pitch wheel, modulation wheel and volume and so although the MIDI model is suitable, there is limited functionality available.

In all cases the user manual for the 3rd party unit needs to be referenced to determine what is required. Contact Oz Inventions if further information is required.

Does it create its own sounds, and can I plug a guitar or other instrument into it?

Thinking of it as an expression pedal will help you understand what it does and doesn’t do. It is designed to work with a 3rd party effects unit, keyboard, or MIDI controller. A plugged in instrument will have no functionality.


How does it act like a musical instrument?
Assuming that pitch is the effect parameter to be modulated, as the sensor is tilted or rotated the pitch will increase or decrease. With a step size of ‘1’ this creates a simple robot type pitch change. However, if each step is set individually to equal the change between say a semitone, as the sensor is tilted or rotated the pitch changes from one semitone to next, just like a musical instrument. The steps can be set to that of a major scale, minor scale, arpeggio or any other step size.


What are the minimum and maximum range settings for?
Limits the range of modulation between minimum and maximum values. For example:

If modulating volume, a minimum setting of zero, and a maximum setting of 127 will provide the full range of volume from no sound through to maximum sound. Changing the minimum setting to about 60 means that the volume will not go lower than about half. Leaving the minimum at zero and changing the maximum to about 60 means the the volume will not go over half way.

This is particularly useful for many effect types. Wah-Wah for example often has a dull tone around the zero setting (heel position) and so raising this to about 30 means that the sound never gets dull.

Pitch modulation is another useful example. By setting the minimum and maximum settings you can get anywhere from a semi-tone to two octaves of modulation (dependent on the effects unit).

Technically, the depth setting sets the minimum and maximum electrical resistance of the internal potentiometer.


Where should the Sensor / Transmitter be positioned?

The sensor / transmitter can be placed anywhere that motion is to be detected. Examples are –

  • Wrist
  • Lower leg
  • Back of hand
  • Microphone
  • Guitar head stock
  • Guitar body
  • On another person (for example a drummer or dancer, so their movement creates the modulation)
  • Anything that is in motion such as a saxophone

Where does the Receiver / Modulator go?
The receiver/modulator connects to the expression jack of an effects processor, keyboard or midi controller, using a TRS type cable.


What is the black rod sticking up at the back?
That is the 2.4Ghz receiving antenna. Being an aluminium enclosure, an external antenna is required for the signal to propagate inside the enclosure.


Does the transmitter have an antenna?
The transmitter has an internal PCB trace antenna, which is suitable for signal propagation through the plastic enclosure.


What size is the transmitter?
Small and light.
Dimensions – 40mm x 40mm x 20mm; Weight – 25 grams


What size is the receiver?
The receiver is a traditional stomp box style, 1590B, enclosure.
Dimensions – L 112mm x W 60.5mm x H 31mm; Weight – 175 grams;


How are the units powered?
The transmitter/sensor uses a replaceable CR2032 battery.

The receiver/modulator uses an external AC / DC power supply. The power supply provided with the unit is a 240v AC input and 12v DC output. However, any output voltage between 9 and 12 volts DC is acceptable. The DC polarity configuration is negative tip.


Can I power the receiver with a battery?
You can. Although there is no space for a battery inside the enclosure, you can use the provided 9v battery clip to power the unit.


Why are there multiple hook and loop elastic straps provided?
A few sizes are provided to enable you to place the sensor on your arm, or leg, or other object, all of which may be various sizes.


The selectable resistances are 12k, 25k and 50kohm. Will 12K ohm be OK to use when my effect unit asks for 10Kohm?

Yes, most likely. It has been tested on many brands and models and it works as expected.

Explanation ->

  • Many effects units ask for 10k ohm or “higher”.
  • Many expression pedals advertised as 10K ohm, actually have a 11K or 12K ohm potentiometer in them anyway.
  • For effect units requiring TRS or RTS configurations the resistance is not so important. The voltage sent back on the tip is proportional to the potentiometer wiper position. And so for example, half way for a 10K pedal will produce the same voltage as half way for a 100k pedal
  • For effect units requiring TS configurations it is more important to use the resistance specified. For example some early Digitech® effect units require a 250K pot otherwise the full range of modulation is not achieved. Line 6® specify 10k for their effect units but 12k works fine. Going too far over this value will means that for some of an expression pedals travel, there will be no change in modulation or unpredictable changes occur. So, yes our 12K ohm expression device will work with most if not all effect units that ask for a 10K ohm or higher expression pedal.