I use this headphone amp for several years. I do not know any other model, but I have a very good headphone output on my sound card (metric halo), so I could compare the difference before and really get to the preamp, it is the headphone, so ...
It performs its job very well: allow me to listen when I save one or artists.
I've never tested the 4 exit at the same time, but the day I need I know I have on hand ...
Totally satisfied occurs.
An entry other than the mini-jack and it was 10/10