The Blue Circle 21.1 preamp has been around for some time I'm surprised there haven't been many members chiming in to help. I checked the archives and saw some positive thoughts on the Blue Circle 21.1 but none with the Blue Circle 21.1 Level 1 mod. Maybe some other forums may be helpful to you.
Let us know what you think about the McCormack once all the mods are done.
Let us know what you think about the McCormack once all the mods are done.