Rubicon 2 TZFM DC offset

Hi there.

I’m having a little issue with my (otherwise excellent) Rubicon 2. It seems that the TZFM input is DC coupled, so any slight DC offset in the modular signal results in a pitch change. This isn’t so much of an issue if the Index is constant (because I can just retune the oscillator), but it can sound pretty badly out of tune if the index varies (say with an AD envelope).

Firstly, am I really correct in thinking that the input is DC coupled? That doesn’t make much sense to me from a design standpoint; surely AC coupled would have been a better choice? (Or, even better, have an AC-DC coupling switch on the front panel). And if I am right, is there an easy mod to install a cap on the TZFM input?

Alternatively, I mainly use a Dixe II+ as the FM modulator. Is there a calibration routine for that oscillator that can remove the DC offset from its waveforms (and most particularly from the sine wave)?

Many thanks!