NEDSP900 Development Board
9
Channel 1
Input (mV P-P)
Gain 1
(Spec. dB)
Gain 1
(Meas. dB)
Channel 2
Input (mV P-P)
Gain 2
(Spec. dB)
Gain 2
(Meas. dB)
2000
0
0
1940
0
0
472
12
12.5
476
12
12.2
348
15
15.2
324
15
15.5
260
18
17.7
248
18
17.8
196
21
20.2
140
25
23.2
112
27
25.0
88
30
27.1
3.1
Setting the Gain for SK7 (Microphone input)
AGC Facility
Selecting the AGC function overrides the Gain setting switches and uses the internal firmware to
select an appropriate gain between 9dB and 31dB, dependent on the microphone signal level.
The AGC operates on voice signal only and therefore only responds to changes in voice level and
not the general audio signal.
Manual Gain setting
A nominal gain setting for an Electret microphone would be about 28dB. This is set by selecting
the gain using switches SW4 – see general section on Gain Settings
4.0
Using the DSP Noise Reduction
The Noise Reduction is individually selectable for each channel. Channel 1 is controlled by SW2
and Channel 2 by SW3.
The Noise Reduction settings are given in the table below with the settings referring to either
SW2 or SW3.
Strength
Setting
Noise
Reduction
(dB)
Switch
1 (On/Off)
Switch
2 (LSB)
Switch
3
Switch
4 (MSB)
Off/Bypass
Off/Bypass
OFF
X
X
X
1
8
ON
OFF
OFF
OFF
2
12
ON
ON
OFF
OFF
3
16
ON
OFF
ON
OFF
4
20
ON
ON
ON
OFF
5
25
ON
OFF
OFF
ON
6
30
ON
ON
OFF
ON
7
35
ON
OFF
ON
ON
8
40
ON
ON
ON
ON
Содержание NEDSP900
Страница 17: ...NEDSP900 Development Board 17 Schematic Diagram Sheet 1 of 5 Output Buffer and Line Driver...
Страница 18: ...NEDSP900 Development Board 18 Schematic Diagram Sheet 2 of 5 NEDSP900 and Control Switches...
Страница 19: ...NEDSP900 Development Board 19 Schematic Diagram Sheet 3 of 5 Balanced Audio Inputs See also Appendix B...
