Yes such devices have been manufactured. Back in the 1970s a company named Burwen put out two units, one for tape hiss, and one for clicks and pops. In the 1980s and 1990s a company named Packburn in Dewitt, NY (near Syracuse) put out the Packburn Audio Noise Suppressor Model 323A, which had a stage for diminishing hiss as well as a stage for diminishing clicks and pops. For a while it was listed in Stereophile's "Recommended Components." Stereophile called the Packburn "the Cadillac of nose suppression units." I ended up getting one directly from the company for $2,400. As the years have passed, it has developed a hum. Whether the hum is an internal issues, or whether there is an externl factor, I don't know. I haven't try to deal with it seriously because I now transfer my LPs to CDs using Sony's Sonic Forge software.
pop and click filters
Does anyone know anything about pop and click filters to minimize surface noise on LPs during conversion to tape (cassette)? I know there are sophisticated software/hardware products on the market now that do this and they may well be the only thing that works but I have heard there were once black boxes that minimized noise without losing too much fidelity. Does anyone know of such products and who made them and where can I find one? Thanks