Page 6
2.3 Pin Functions
The basic operation of the NEDSP pins is described below. More details may be found later in this
manual.
Pins 1-3 DSP Filter level set -These pins allow remote setting of the noise cancellation level. If these
pins are used, then ensure that the appropriate on-board pre-set solder jumpers are
removed (JP1
–
JP3).
Pin 5 Supply Voltage - Supply voltage 5 V to 15 V DC
Pin 7
0V - This is the 0V pin and acts as a Star Point for all Audio and Power Grounds.
Pin 8 Noise Reduction On/Off - Connecting this pin to 0V inhibits the noise cancellation. Leave
this pin floating or tie it to +3.3 V to enable noise cancellation.
Pin 9
Audio Input - Audio Signal to be processed
Pin 10 Audio Output - DSP Processed signal from the module.
For optimum performance, keep all leads as short as possible. Use screened leads for the audio
signal and make sure that the 0V pin is grounded correctly with all signal grounds being reference to
this pin.
2.4 Controls
The audio level control potentiometers VR2 (Audio Out) and VR1 (Audio In) provide adjustment to
audio levels entering and leaving the module. Both controls are pre-set at the factory such that a 1V
p-p input provides a 1V p-p output with the Noise Reduction disabled.
To set the Input Level correctly, adjust VR1 until the
‘O
verload
’ indicator
(LED1) just illuminates.
Then back off the potentiometer until the LED extinguishes. Turning the potentiometers clockwise
increases the levels.
2.5 Electrical Characteristics
Output impedance: 1k Ohms typical
Input impedance: 7.5k Ohms typical
Analogue Characteristics
Parameter
Description
Min.
Typ.
Max.
Units
Vin
Supply Voltage
5
8
15
V
Iin
Supply Current
15
20
mA
In
Audio Input Signal
10
500
mV (rms)
Out
Audio Output Signal
1000
Digital Characteristics
Parameter
Description
Min.
Typ.
Max.
Units
VHigh
High Level Input Voltage
-
3.3
5
V
VLow
Low level Input Voltage
0.8
-
-
V
