Jinx wrote:
>> LM324's? No problem!  Newer stuff is, well, newer stuff!
> 
> What turned out to be an op-amp problem drove me batty
> yesterday. Making an electret mic pre-amp (part of the ISD
> project). Simple enough, but couldn't get rid of a spike that
> always happened on the rising quadrant of a wave cycle. Had
> the circuit apart, added things, took things away, single-ended
> supply, split rail, hit the web, no change. Only when I swapped
> the op-amp for a dirty old 741 would it work cleanly. NE5534,
> TLC271, TL071, no good. All had the spike. Weird and very
> frustrating
> 

That sounds like crossover distortion.  It happens when the output 
switches from sourcing to sinking current.  LM324's and the like suffer 
from this but it's easily cured for the most part.

Try hanging a 1K resistor from the output to the negative rail; this 
will make the output try harder and should minimize the spike.
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