Here's a tip!

Transfer your 78's to CD as follows...
Play them at 45rpm (or 33 if you've the time) into your recording software on your computer (NOT via cassette!), then use the software to speed them up. That way you obtain the best signal transfer - decks with 78 on them aren't usually very good - and you'll also automatically lose some of the background noise, because its frequency goes beyond audible (especially using 33)...

Okay, there's still some to lose - but 78's are supposed to sound like that, aren't they?!!