I have 3 and they are modded. I had Amek replace some of the pots. As for mastering??? it has it's place. It's a colored compressor that errors on the side of gentle. I like the transformers in it and i'll add it in for a bit of color but not really anything else. the needles almost don't even move. I use them mostly for surround stuff as I like their gentle nature in this format. But for 2 track stuff, they aren't much use. For individual elements, the are quite good and versatile.