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Two of the three FETs have silver paint on their face. We painted them to indicate that these two
FETs have been "matched" to each other. This means that the gate-source turn-off voltage of these
transistors were measured to be within about 100th of a volt of each other. This allows both
sides of the circuit to be balanced very closely, achieving very high common mode rejection,
which results in a very quiet microphone.
Transistors are polarized, meaning it is important which way they fit into the holes. The
component side of the circuit board shows an outline of the transistor body in the correct
orientation.
a. Place the silver-painted FETs in the locations of Q1 and Q2. Either silver FET can be Q1
or Q2; it doesn't matter which one goes in those locations as long as they are both silver
(14,15). On the bottom of the board bend the leads a bit so they won't fall out of their holes.
b. Place the other FET in the Q3 location (16). Please be mindful of the correct orientation.
Bend the leads of Q3. Turn the board over, solder and clip all the transistor leads
(17,18,19).
14
16
18
15
17
19
12
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