Here is the summary of these products on the Nakamura site. if you go in and translate the Japanese for the NXT-1, it has the same functions as the NXT-2AK. It has TRRS inputs and outputs. It can do full balanced drive, and like the NXT-2AK it can also convert single-ended to balanced (which is common function of isolation transformers). Where it differs is that unlike the NXT-2AK, it is not specifically advertised as suitable for pure single-ended use. However that may just be an omission in the short Japanese description. (EDIT: Google translate also has its limitations. Reading between the lines, I think that it functions just like the NXT-2AK, i.e. suitable for purely single-ended use.) The obvious difference between the NXT-2AK and NXT-1 is that the latter does not have a TRRS 2.5mm output which is suitable for headphones terminated for the AK240. (An accessory cable is available for the NXT-1 that adds that function.) If you want a pure single-ended Aclear Porta isolation transformer, the model is the NIP-05TH. It doesn't look as nice though. The NXT-1 and NIP-05TH are both an ounce lighter than the NXT-2AK. (The NXT-2AK is the second densest thing that I own; only the special dive weights for my rebreather more closely approximate a black hole.) Lighter is not necessarily better though. Good transformers are inherently heavy. I can only say that the NXT-2AK is a beautifully made product and sounds great with both my PAW Gold and M. I am happy with it.