Re: Deriving 3v at 30mA from 5V Supply
It might well do, but I'd be more inclined to the view that excessive hum on the output of a 7805 or the like could be the result of poor ground wiring layout and/or lack of headroom in the input voltage causing the regulator to drop out on input ripple voltage troughs.
A 7805 requires at least 2.5V I/O differential to avoid dropout, so (for instance) an 8V input with 1V p-p ripple on it would be right on the edge.
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