-5V supply
The LT1931A with R71: 82K and R70: 30K is giving -5V34 instead of -5V
The calculation noted on the schematics is based on the LT1931 chip, not
the LT1931A.
R70 should in principle be replaced by 33K, but it could be that this
precision is not needed by the ADA4899 chip.
TODO: confirm if -5V34 is within specs for the ADA4899.