Decco as DAC only?

Hi all - I am currently using my Decco as a dac/pre alongside an integrated amp. I would like to bypass the Decco's pre-amp, and use it solely as a DAC with line out to the integrated amp. Is there a way to do this with the 1st gen Decco?

If not, any advice regarding volume control between the two amps? It seems that turning the decco way down and the integreated way up I get a very clear sound but it lacks body. Doing the opposite seems to increase distortion but sounds more full. So far I prefer the former