I was thinking of using a small trim pot in the feedback loop of an op-amp (in series with another resistor, i.e. 5k trim pot with a 50k resistor in series, both compromising the total feedback resistance) pre-amp to make some fine adjustments to the gain. Will this have any detrimental affect on amplifier noise (I was wondering if the noise in a trim pot might be worse than the noise in a typical resistor). Thanks.
Use cermet preset rather than carbon for the lowest noise perhaps? If its in series with 50k the 50k is likely the dominant source of noise anyway, carbon or not.
With the parallel combination the trimmer resistance should be the large value if its only for small adjustments.
If you make the trimmer the bottom leg of the divider (assuming non-inverting amplifier configuration), then if it goes open-circuit you still have feedback from the upper resistor. So you can have a series arrangement of resistor and trimmer for the lower leg for the adjustment and fixed resistor for upper leg.
With the parallel combination the trimmer resistance should be the large value if its only for small adjustments.
If you make the trimmer the bottom leg of the divider (assuming non-inverting amplifier configuration), then if it goes open-circuit you still have feedback from the upper resistor. So you can have a series arrangement of resistor and trimmer for the lower leg for the adjustment and fixed resistor for upper leg.