I bought the DX90 from a local dealer, after failing a bid on a used HDP-R10 last week from yahoo.jp
Also received my Yamaha EPH-100 today from mail. So I have got 2 new toys trying out tonight :->
I would say the DX90 does sound very nice, with the same sound signature of my Audio-gd NFB-1. I would say the DX90 amp section is good enough to drive low impedance IEM, but does not have enough voltage swing to drive high impedance ear bug like my 150ohm PK1 clone. The gain switch make just a bit of volume difference when driving the PK1 clone.
The quality improvement through LINE OUT to the Arrow 4G amp is quite obvious. The PK1 comes alive, and there are much better instrument separation, layering and sound stage with the EPH-100.
And yes, the EPH-100 is a good match (with or without the Arrow 4G) with the DX90. Very good dynamic!
Will do more burn-in to both the DX90 and EPH-100 to see if the amp section will improve, but I won't expect any major improvement. I also think -75db channel separation is kind of low for the amp section given its dual mono design.
Overall I am very happy with the DX90, as I already expected to use it with the Arrow 4G before purchase.
Edited by borrego - 5/5/14 at 10:36am