I have the 4T 3G, and 4G arrows. The 4G and 4T i think are virtually the same, but the T stands for treble boost which I don't typically use. In relation to the question above my post, I think the 4 series does improve the imbalance at low volumes, but on my FitEar A111's at really low volumes there is a slight imbalance, although it isn't notable with other IEMs or over the head models. Overall the Arrow is my go to portable amp still, I prefer it over other models in it's area such as the RX Mk2 and Pico slim. It also has the best fit/finish of the aforementioned models in my opinion.
T = Tube-like