I've bought and tried the Audio-GD NFB15.32 (recommendation from Head-Fi) for a few days with a pair of Mad Dogs. My impressions are so negative that I'm willing to part with it. Compared to the $150 Focusrite Scarlett 2i2, its worse in every single way but consumer electronic connectivity.
Positives:
- Connectivity is quite good, though there is no analogue input. Its good enough to hook a console and desktop however.
- Its built well and is pretty handsome. It doesn't have good fit and finish but for the price you can't expect everything.
- The bass is pretty full and solid.
Negatives:
- Its really deep for what it is. I cranked it open and the design that necessitates the space looks excessively complex like most "audiophile Class A designs".
- Speaking of Class A, it gets stupid warm/hot even if it isn't doing anything. There isn't any ventilation to speak of so I guess the case acts as a heatsink? It gets hotter than my power amp and it doesn't even have tubes. Definitely wouldn't feel too confident running it in the Australian heat.
- The filter switches don't do anything. They probably do but blind testing suggests that I can't tell anything. Same goes for the oversample feature. With certain content, you have to decrease the oversample for the amp to actually output something that isn't silence or white noise. If anything, this might suggest something about DACs that claim insanely high bit and sampling rates...
- There's something about the midrange and highs that just sound...off. I can't explain, it sounds muddy and sometimes the highs just sound excessively sharp. To confirm, I listened to Reggatta de Blanc and yep, Copeland's snare and cymbals sound dreadful.
For the $300 or so bucks its selling for, I have no idea why you would pick this over, say, an O2 + ODAC (which does actually sound pretty good) or an audio interface unless you wanted a preamp that isn't USB powered.