Not that I'm going to tell you how to suck eggs Tony, but.....You can mod a thing to death sometimes. Make sure you have another one to compare to everytime as reference, because sometimes what appears to be a foreward step can sometimes just be different.

To be honest I'm not even sure how they can justify £600 for the Minimax in the UK. A choke regulated, valve rectified 2x12AU7 pre (amplification/buffer) similar to this is  for about £300