Dear @mazikrav: You can do it but that unit will make a " terrible " degradation to the audio signal.
Its specs are really very low-fi:
Frequency response: 50Hz to 15kHz
Total harmonic distortion: 0.5%
These is what owners posted ( from those old times. ) on that unit:
"""
The problem with the NX-40 is that it was a super cheap unit that dbx introduced in the early 80s that was based on their new (at the time) dbx ICs. Unfortunately the NX-40s never worked very well. I know this becuase I used to own one when I was a kid.
They overload super easy, making it more diffcult than it should be to set your levels. """"
Regards and enjoy the MUSIC NOT DISTORTIONS,
R.