There are actually several different, unrelated problems being referred to in this thread. If a record has been really, thoroughly cleaned and rinsed deep down, the remaining "ticks and pops" are surface noise resulting from minute scars in the vinyl itself. This is often tolerable to a surprising degree if it is not too severe, depending on the type of music in question, and how "hot" the record was cut volume-wise, because the noise is not well correlated with the recorded signal. As for "rolled" frequency extremes, this is determined by the recording and/or mastering process, and is not the result of normal degrees of wear or dirtying of the record. The type of distortion that I suspect is being called "gross and obvious" in the original post can be another story. Highly dependent on the level of the recorded signal's peaks, as well as their frequency range, this has little to do with surface contamination. This distorted sound is hard to bear because it is well correlated with the recorded signal, and is the result of the record's having been much played in the past on mistracking, usually old and inexpensive equipment. The subsequent damage to the vinyl is worst on highly modulated peaks, even though the record may appear to have been kept decently clean, and be mostly free of surface noise. On classical music, I myself always get rid of these, but will keep a good record with a little surface noise until a better copy comes along. With older rock and R&B or jazz, somewhat higher levels of noise are acceptable. However, for response roll-off a CD remastering might be the best fix available. (Though I do sometimes find that "old-timey" sound can be ingratiating on certain material, and can even grow to enjoy the "scratchy" sound of some genres of antedeluvian 45's and 78's, which won't skip like an LP - ya gotta love that giant ol' groove!)
