MOTM

My guess is that it's probably a relict from a circuit that used an opamp with higher input bias current.
The MXL1014 would probably just work as well with the + input tied directly to GND.

Bad effect? *Theoretically* that resistor increases noise, and EMI receptivity, if not bypassed with a cap. But certainly not here 
in this application, summing large controll voltages, so I can't really think of any bad effect!

JH.


>Correct, not critical, 15K to 33K will work, 5% ok.
>
>Bonus: what is the specific *purpose* of this resistor, and ...
>Bonus #2: what "bad effect" results from using it (but is compensated for later in the design, and what is THAT compensation?)