Just for clarity... ART have two similarly-named, but completely different products.
The
CleanBOX II is a dual-channel passive box containing a pair of audio transformers connected with TRS sockets in and out. The transformers provide galvanic isolation between the line level inputs and outputs (to break ground loops) and also convert between balanced and unbalanced connections on either side.

It operates at nominally unity gain (ie, the output level is the same as the input level) and is ideal for converting between unbalanced outputs and balanced inputs, or vice versa, and for breaking ground loops.
It has a slightly more expensive (but far more versatile) sibling called the
DTI which is essentially the same thing in a differently shaped box with a plethora of different parallel-wired connectors on each side (XLR, TRS and RCA-Phono). This makes it far more convenient for connecting different devices as well as for splitting and duplicating signals. (I have five of them at the last count as they are so extremely useful).

Then there's the
CLEANboxPro which is a dual-channel 'level converter'.

It looks similar to the DTI, but it has volume knobs on the front and no TRS connectors!
Internally, this is a very different device, though. It is an active product that requires external power, and it is intended to connect unbalanced domestic equipment like video recorders etc to balanced professional equipment. To that end, it receives unbalanced (RCA-phono) inputs at a nominal -10dBV and provides +12dB boosted balanced outputs at +4dBu. It also receives balanced +4dBu inputs and attenuates them by 12dB to provide unbalanced outputs at -10dBV. (The actual gain is adjustable.)
The nature of the active circuitry means there is no galvanic isolation between inputs and outputs. It's a useful box for converting between consumer and professional equipment connections, especially if you need to also adjust the signal levels, and can also be used to interface between pro gear and fx pedals. But it will not help with ground-loop problems.