Just putting together my Pedalshield and I was curious why you were using 1N5187 diodes which are described as ''fast recovery'' and ''Military qualified''.
Thanks
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We selected the 1N5187 because they are cheap, easy to find and they were used in
similar applications
with good results.
These four 1N5187 diodes are low-voltage-drop Schottky
clamping diodes
. The clampling diodes will prevent the input guitar signal to be more negative than –0.24V and more positive than 3.54V.
The Arduino Due ADCs can work with signals from -0.3 to 3.6, but overcoming these limits can damage the ADCs.
The series 4K7 resistors R9 and R10 will limit the current though the diodes, lowering the diodes VF to a good value to protect the ADCs. At the same time these resistors values are low enough to keep a good source impedance for the ADC (remember that the
Atmel ATSAM3X A/D datasheet
page 8 mentions that the source impedance must be lower than 10K)
