Moog Theremini plays with phase shift of 90 degrees

Hello I am new in this great community and unfortunately my #1 post will be on a technical problem on my Theremini. Recently I bought from Thommann my first Theremini. I started recording it and just now I realized that it's signal is 90 degrees shifted. Is there any ideas on that?

Phase or time shift occurs the whole time in all kinds of circuits due to the (positive or negative) delay created by Resistor-Capacitor interaction. But that is not audible and the phase angle varies most times with the audio frequency. Having a constant 90° phase shift throughout the whole audio spectrum seems highly improbable to me. How did you detect it?

Please explain the phenomenon which you experience in a more detailed way, please.

Some of the earlier DACs shared a single internal DAC for both left and right channels, which would result in a frequency dependent phase shift (worse at higher frequencies).  Is it something like that?

Basically, if a time delay between the left and the right channel would occur at the Theremini, it's even not worth discussing it, since the theremin is basically a monophonic instrument and should even not have two different output channels. 

The Theremini is and remains cheap digital crap which has (besides the basic gesture control) nothing in common with Leon Theremin's concept, so it shouldn't be mentioned in these forums!

Well, it does have stereo out, so a phase difference there could be an issue.  We don't really know what the OP means yet.

I don't think I'd come down quite that hard on the Theremini.  It does sense capacitance via LC oscillators, and probably uses heterodyning for the pitch operating point.  Moog Inc. could have done a much better job on it though, and that's the real shocker for me.