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NEA Aftertouch Sensor Installation Instructions

Thank you for purchasing our aftertouch sensor. We think that you will find it to be superior

to the original in terms of expressiveness and feel. Please follow these installation

instructions to ensure the best performance from this sensor. Have fun!

Fig 1. NEA Aftertouch Sensor

Pictured in figure 1 is an NEA aftertouch sensor and an additional sensor for longer

keyboards. If you are installing two sensors in a synthesizer such as the ARP Quadra, the two

sensors should be wired in parallel. This means that you need to twist together the red and

black wires of the two touch sensors.
Before installing the sensor bar, make sure that your key bushings have been replaced

in the last 10 years. If they are dried and cracked, the aftertouch will not be smooth or even

across the keyboard. The metal tongues that the key bushings mount on should all be straight

and aligned to the same height across the keyboard. You do not want some keys to be higher

or lower than neighboring keys.

Fig. 2 Key:in rest position

Fig. 3 Depressed key (Aftertouch not engaged.)

We recommend removing the plastic key tops when doing this installation, as it makes

accessing the metal tabs inside of the keys easier.

It is important to understand a little theory on how this sensor works. Figure 2 shows a

cross sectional diagram of a Pratt Read keyboard mechanism. In this diagram, the touch

sensor bar is mounted beneath the keyboard frame. The bar can just as easily be mounted

above the keyboard frame. To do this, attach the jnuts to the bar, and not the keyboard

frame. We recommend mounting the bars as shown in figure 2. Figure 3 shows the key

mechanism with a key depressed. It is important to note that when a key is depressed at a

normal playing velocity (aftertouch not engaged), the key should be blocked from touching the

felt of the sensor bar by the rubber key bushing. The key sheath should not begin contacting

the felt of the sensor bar until you begin compressing the rubber bushing by pressing down.

Cardboard spacers are used to adjust the height of the bar across the keyboard so that the
geometry is as described above. If a note is too sensitive, adjust the height of the key by

moving the tab that the bushing mounts to in the upward direction. This will cause the bushing

to block the key before it hits the felt. If a note is not sensitive enough, adjust the tab

downward so that the key makes more contact with the sensor when aftertouch is engaged.

The best way to test the uniformity across the keyboard is with an ohmmeter. Connect the

Ohm meter to the red and black wires and depress each key to get a reading. The resistance

should be very high until aftertouch is engaged. Adjust every key using the techniques

described above. When satisfied with the response. Reinstall keyboard in to synthesizer and

wire sensor appropriately.

Fig. 4 Sensors installed in an ARP Quadra keyboard

When installing on synthesizers that did not have a touch sensor previously, it may be

required that you drill additional holes on the underside of the synthesizer to accommodate

any new screws that must be added for stabilization purposes. We usually use a tapping drill

bit that will thread new holes onto the sensor bar from beneath the keyboard.

Good luck with your installation and enjoy your new sensor!