Bug:
R26, R29, R37 R40 must be a bridge instead of 10K.
improvements for better noise ratio:
install at U4 and U5 a OP275 opamp and swap C1 from 22p to 33p.
furthermore install a 33pF capacitor at U4 and U5 between C5 and C6.
Guide: (extract the Partvalues from the Schematic on the last page in this document). not nice- but what can we do ?
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