Hello Didier,
Sent you a PM (to your hotmail) in case you have further questions.
Shortly, hopefully this is not too far off topic for this section:
I built a replica of a Meazzi tape echo, of course no tape heads or motors. Then adapted the eTap2HW DSP code in the Spin Semi OCT module to separate the head playback and feedback head outputs for processing those through the Meazzi valve circuitry. This is how it was done in the Meazzi. Concept is simple though a lot of work.
Hope that helps.
Regards,
Johan.