[Elecraft] KNB1 question

[Richard Lim]

Can anyone explain to me the difference between Rev C and Rev D boards of
the KNB1?  I'm staring at the schematics and it seems that later versions of
the NB ie:Rev D or later, have two additional caps to ground in the noise
amp section where as on Rev C they are not present. I'm wondering if there
is any functional difference between these two boards or if the additional
caps (C12 and C13) are there to correct an error in the board. Inquiring
minds want to know.
Rich

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73 DE KQ9L K2/100 #3232 K1 #1669