These boxes are great for mixing and/or recording but need some work if you want to use them in a mastering situation.
The tubes need to be replaced with a matched set for noise and output and you would probably also need some type of line level adjuster to match them up perfectly. Read more
Not entirely out of the question and opens up the possibility of altering the tone with different tube types much like a guitar amp.
Out of the box, the bottom end sounds warm, full and very close to the originals. High end, not so much. A touch harsh even when using the full broad bandwidth setting. 8K and above, this is less noticeable. Cut functions are very good on both sides.
The stepped pots are a nice touch. Very small increments and easily logged but feel slightly on the cheap side. Probably easy to switch them out.
Overall, a great purchase for the money.