So, the data is now flowing in nicely.
Teabox entry xlr nr 1 with photo cell – and accurately presented in teabox decoder software (see pic).S/PDIF is channel 9 in the RME fireface 400. Seems to work correctly.
But the spikes in M4L teaboxOne remain.
It has something to do with the fireface i guess.
any suggestion is welcome!