problem rekordbox performance low volume on mac

What are you using as your output device? Or are you sending the audio to the internal sound card?

directly the cdj player connected in usb and then connected to a mixer  pioneer 900nxs2 in digital

I don't understand -- you're using a DJM900NSX2, it has a gain knob. Turn it to adjust the signal level for that input...?

wow gain knob......obviously it has gain knob, but the question is why with the mac the hid advanced output of the cdjnexus2 is -6db and with the pc is 0db like the usb stick? is there something to set in the rekordbox over mac to adjust the volume

No - when you are using the audio outputs of the CDJ or DJM as the soundcard, that's the output level. Is there a problem with adjusting the gain?

yes i have to gain a lot with the mac like plus 6db, the same system with the pc the volume is exactly the same if i use the cdj2000 with usb sticks

Sorry, I still don't see what the problem is?

is something that fails in rekordbox for mac, because same rekordbox performance on pc is 0db at the output same volume of the usb sticks. if you gains a lot you add distorsion is a physical thing....so why the rekorbox on mac is minus 6?

The amount of undesirable signal or artefacts possibly introduced by adjusting the gain by +6 on a digital source is minimal. I'm sorry it doesn't match the levels when used as an audio interface for the PC or direct from a USB / CD source, but this isn't exactly a "problem".

normally we said that apple is better but in this case the asio pc driver is better

¯\_(ツ)_/¯

I got the same problem on MacBook Air

using rekordbox without any controller low Volume against Itunes 

Have you tried adjusted the system volume (using the volume buttons on your keyboard) as well as the the volume slider in Rekordbox? The system volume is a separate beast from the app volume controls, this goes for both iTunes and Rekordbox.

In Performance Mode go to Settings - Controller - Mixer - Output level - Headroom - set it to None. Now speakers will be blowing full volume

Thank you!!!