.. I found it, at least!
This schematic was published on "Suono", an Italian magazine, no November 1993.
The schematic was directly derived from the PCBs, but some parts are not drawn - such as the NE5532 integrator, but the audio circuit should be complete.
The bias currents are 1.15mA, 12mA and 1.3/1.9 for the 1st, 2nd and power stages: for this one were noted two values, for left and right channel respectively.
Hope this helps.