I have 2 vintage analog units in my stash of black boxes that some times show up on ebuy.
"DNR / Dynamic Noise Reduction model 450" made by Advanced Analog Systems. This is a variable bandwidth system that reduces the bandwidth on low level signals and as the amplitude rises the bandwidth broadens.
Helps some on surface noise does nothing for pops and crackle. Made for consumer market.
A similar unit designed for professsionl use is the Dynafex DX2 and reduces noise with bandwidth reduction. It has the advantage of a brilliance control which activates a form of Aural extiter for the high end signal after noise reduction providing adjustible brilliance being added back into the processed signal.
I have found the end results more to my liking with a analog transfer, digital noise/pop reduction. however.
d nelson ward
Beautiful Music you will never forget, at; http://www.americanbeautiful.podbean.com/