Page 14
Add solder across each
of these jumpers as
neccesary
Overload indicator
The Overload LED indicator will not activate when using the module with microphones, its only
provided to notify the user that they are overloading the DSP input. This is very unlikely to happen
even with a MEMs microphone.
Setting the gain on the NEDSP1901-PCB-MIC
To access the gain links, the plug-in module (IC1) needs to be removed from the socket on the PCB.
This should be carried out within an ESD safe area with an appropriate ESD wrist strap on the
operator. Locate and identify the 3 off sets of Gain setting pads as shown on fig 1 below. It should
be noted that the pads marked CH1 G0 are already linked as part of the 1901 PCB assembly. These
pads may be disconnected using a sharp scalpel to cut the PCB trace that joins then.
Note:
Do not
cut too deep as this PCB has several layers and you may sever traces on the underlying PCB layers.
Re-connecting CH1 G0 is carried out using a solder link. The other two sets of pads are highlighted
to the lower right of the module layout (Fig 1). Both sets of pads need to be linked with solder to
enable them to get 30 dB gain. If another gain setting is required, then refer to the Gain Settings
table on page 5 and identify those pads that need linking. If the gain needs to be reduced, then the
solder link needs to be removed.
Track may be cut with scalpel (CH1 G0)
Remove all links and link these pads for
AGC operation
+3.3 V
available for
electret use
via 2.2 k Ohm
resistor.
Fig 1
View of jumpers and component locations underneath IC1 (remove to access the jumpers)
Picture showing the main
DSP module removed from
the NEDSP1901-PCB-MIC
module revealing the
various jumpers that are
required to get the correct
gain settings for the type
of microphone used.
