One more time: burning an audiocd made of 75 minutes of music I did not get more than 1,000 C1 errors by the "old" TY media.
Cakebox after cakebox, month after month, I noticed a slow but constant decreasing in matter of quality.
I am almost sure that in a couple of months, when I wll buy a new cakebox, the scannings will be different, and the media will get worse
Anyway, to answer your question: the scanner is the Premium II too and the scanning speed is 4x like advised by Plextools: higher speeds than 4x are not realible.
I also tried 2x, 4x and 8x burning speed but it was even worse. The old rule to burn audio at the lowest possible speed is not a good one anymore. Not by using nowdays media.
There are several threads here about the "ideal" speed for audio, and 16x seems to be to perfect match!