Of course you need to grab the repro head outputs directly: typically this is done one of two ways: direct connection to the head outputs in the headblock or at the headblock connector itself; or at the audio card cage repro head connections (often removing the repro cards and using a “bypass” or extender card to connect the the required cables (shielded twisted pair terminated in a male XLR for each channel).
It’s not particularly difficult, and Any good Audio/tape machine technician should be able to assist you with this if needed.
(It is also possible to install a very high quality DPDT switch designed for very small signals at/in the headblock to allow switching between the original repro electronics and the outboard electronics- but while an interesting comparison at first I predict you will cease using the inboard electronics within minutes or hours and use solely the outboard NextGen connection…)
It’s not particularly difficult, and Any good Audio/tape machine technician should be able to assist you with this if needed.
(It is also possible to install a very high quality DPDT switch designed for very small signals at/in the headblock to allow switching between the original repro electronics and the outboard electronics- but while an interesting comparison at first I predict you will cease using the inboard electronics within minutes or hours and use solely the outboard NextGen connection…)