I just purchased one of these, refurbished by the seller. There are probably better decks out there but I haven't had the pleasure of hearing them. I tested the recording and playback sound quality as soon as I could after receiving it.
When using the TD4800 I cannot hear any difference between a cassette or a CD. None. BTW, the cassette I tested with? It's about 40 years old and this is the first time it's been played in about 26 years.