+1
I have my Axe-FX ultra for over a year and used in many different scenarios - direct to the board, to the tube poweramp/mesa 4x12, 4cm with my F100 head, efx return and it shined every single time...
Best piece of gear I have ever bought,
Mik.
I had the same kind of problem with my F-100 head and it's parallel loop when I needed to use it in 4cm with my Axe FX ultra. Solved it by soldering 2 wires and turning the loop into the serial one. Took whopping 20 mins to do so.
It is a very popular mod and lots of examples/guides are out...