Hi, new here today (01 post count is probably a giveaway
). As it happens my Topping NX1 arrived today. I came across them on eBay last week, and got mine from a UK seller for £21.99. Primarily it's for using with my phone - it'll ease the drain on the battery when listening to music which I do quite a lot. I'll also use it in the car - the phone's audio output doesn't really have enough signal for the aux in I've hacked into the car stereo. With the NX1 on high gain setting it'll easily drive the volume to hearing endangering levels.
Anyway, I did a Google search to try to find a bit more out about the NX1 and the first link led me here. Having read through the thread, I decided I'd give it a spin against my hi-fi headphone amp with a pair of HD580s. My home amp is a World Audio Design (ECL83 powered) HD83 which I built back in about 2001. I dropped Leonard Cohen's "Ten New Songs" into the Opus 21 and spun it on "Boogie Street".
For a £20 headphone amp, the NX1 is none too shabby. It's fairly neutral in presentation, maybe a touch forward in the mids, with good detail. Breadth and depth of soundstage isn't bad at all. It doesn't quite have the transparency of the tube amp or the same level of three-dimensionality (the layering of the vocals in the intro isn't as well defined) but then I'd be pretty disappointed with my HD83 if it did. For it's intended use, it's a bargain. I would never have believed a £20 headphone amp could sound this good. At 300 ohm impedance, the 580s aren't an easy drive, but the NX1 has tons of headroom - I measured 99.5 dB(A) in the earpiece with my sound meter before really bad distortion set in.
Incidentally, the high gain setting sounds so much better than the low setting, even when volume matched......