The nw2s::io has become the unsung hero of hundreds of studios around the world. People say it makes all the difference in their workflow. It's completely relieved many others of grounding issues that cause hum and buzz. The bottom line is that it sounds great and creates an easy to use, consistent integration point with the rest of your studio equipment.
To match studio levels, the balanced 'io provides 6dB gain reduction for audio from the 3.5mm jacks to the balanced DB-25. In practical terms, what that means is that a VCO patched directly will it near-ideal analog to digital levels of about -15dBFS depending on how your interface is calibrated. VCAs and overdriven filters bring the levels closer to -6dBFS. Hot levels without making it too easy to overdrive your ADC inputs.
When routing in from the DB-25 to the 3.5mm jacks, the signal is increased by 6dB. This will keep your modular from clipping most line-level inputs and provides extra gain when bringing studio signals into your modular.
The balanced version uses high-quality line drivers and receivers from THAT Corp which are individually laser trimmed to provide the best common-mode rejection and that run on a dedicated on-board 18V hybrid power rail for headroom far above any signal that even your modular can generate.
An optional rear-routed cable allows you to route signals behind your rack as well. Since the 'io is DC coupled, it also works great as a CV/gate interface if your audio interface supports it.