Any electronic piece can cause distortion. Mic - see above. Preamp, yea, esp. the $5 worth of electronics that can come with cheaper interfaces. Even your compressor can … One good thing - if your converter overs you will notice.
But really, you have to go down the list from mic to converter back to mic, testing each iteration. And tho I don't sing, singers are usually like every other musician and play louder than they practice. Might be the problem.
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