I have the same problem. I have not solved the problem yet but I think this is the solution:
U need a EUROPEAN version of the speedbox II. Speedboxes sold in the US are
also designed to assume they are driving turntables bought in the US and hence
are designed to generate 60Hz at 45rpm. What we need is a speedbox designed
to generate 50Hz at 45rpm, which are the european models.
I have ordered one from Germany and awaiting its arrival. If it works (I hope it does) I will let everyone firstname.lastname@example.org