Hi! After several weeks I finally managed to find a root scenario where I can found the problem.
It seems that all comes when I print using a ICC profile from OSX instead of choosing a photo paper. For any reason that's the root cause no matter the paper I use.
In the screen shoot the big print is using a Mat Fibber paper from Hanemuleh with the correct ICC profile and using MIRAGE software (but it never minds, I've tried with Capture One, Canon software and other software packages in all cases the same result).
The small one doesn't have the magenta cast but is using as output configuration semi glossy paper over the same Hahnemuhle Mat Fibber paper. My interest was to check the kind of black and whites and, as you can see, they are good, that's it, without the magenta cast.
So that's the problem. For any reason when I choose a ICC profile the output has a magenta cast. I tried with ColorSync, without ColorSync and leaving the printer the control but without luck. I reinstalled the ICC profile as well.
If I choose semi glossy paper it prints with good black and whites, no matter the real paper I use (real semi glossy or a hahnemuhle fine art paper).
No idea what is happening. The only thing I know is this: If I configure the printing with a photo paper (semi glossy in this case) it works. If I configure the printing using a ICC profile it don't.
Thanks for any clue.
