Thanks Hoki Toki!
Yes it is. I tried all of the inputs: Line 1, Line 2, CD, Phono, Tuner, but none worked.
Hi Bayou Texan,
thanks! Yes, it might be an issue of the signal level, which could be too low for the HIFI input.
Anyway it is not dramatic, because I can play over the power output and speaker cabinets,
and use the HIFI as a play along.