I recently made a LM386 op-amp based microphone preamplifier(i know its not a 'true' op amp tho) but it pics up the engine noise. I know its picking up the 12V+ line noise so i am making a linear voltage regulator, similar to the voltage regulators used in a cd players pre outs to clean up the voltage. from what i see, the easiest is to make the LM317 linear voltage regulator. does anyone else agree? or does anyone suggest any other?