The Audio-gd NFB-12 is a desktop combined dac/amp with a compact form factor. It is advertised as having a warm - but still detailed signature.
About Me (preamble)
I'm a 44 year old music lover. I don't say audiophile - just love my music. Over the last couple of years, I have slowly changed from cheaper listening set-ups to my current entry/mid-fi set-up. I vary my listening from portable (i-devices + amp) to my desktop's set-up (PC > coax > NFB-12 > HP). My main headphones at the time of writing are the Sennheiser HD600s (superb IMO) + a modded set of Alessandro MS1i. I previously owned Beyer DT880, Shure SRH840 and 940 + various IEMs. I have very eclectic tastes listening to a variety of music from classical and opera to grunge and hard-rock. I listen to a lot of blues, jazz, folk music, classic rock, and alternative rock. I am particularly fond of female vocals. I tend toward cans that are relatively neutral/balanced - with a slight emphasis on the mid-range. I prefer a little warmth in the overall signature. I am neither a bass or treble head. Current amps = NFB12, GoVibe PortaTube, Fiio E11. previous desktop set-up was a Fiio E7/E9 combo.
Physical dimensions
The NFB-12 measures 44mm high, 163mm wide and 225m long, and weighs in at approx 2.5kg.
My version was latest with the 9 user adjustable digital filters - more on those later.
About the Unit - Main Points (from the website)
Dual WM8741 inside
Dedicated DAC + HP/Pre amp
Dedicated DAC variable and fixed line level
24Bit / 96KHz USB input and 24Bit / 192KHz Coaxial input support
Front plate:
Output switch: HP / Fixed DAC / Variable DAC
Gain switch: Low gain (+0DB) or high gain (+12DB).
Alps volume knob: Controls the volume level of the headphone or variable DAC output.
Source Selector switch: Select source between USB, coaxial and optical.
Rear plate:
Power socket: For power input and power ON/OFF switch.
USB socket: For USB input.
Opt socket: For optical input.
Coax socket: For coaxial input.
DAC out sockets: For dedicated DAC output (fixed or variable).
Technical Info
S/N Ratio - 118db
Output Level - HP output : 10V RMS, Var output : 10V RMS, Fixed output: 2.25V RMS
Output power (H/P) - 3500mW/25 ohm, 1800mW/50 ohm, 900mW/100 ohm, 300mW/300 ohm, 150mW/600 ohm
Output impedance - 2 ohm / both HP & DAC output
Input Sensitivity - 0.5 Vp-p(75 Ohms, Coaxial), 19 dBm (Optical), USB1.1/2.0 (Full Speed)
Frequency - 20Hz - 20KHz
Power Consumption - 10W
Accessories
AC power cord, USB cable, optical cable, bag with digital filter jumpers + replacement LED, and a 4 way connector (which I still haven't worked out yet). Documentation is non-existant, but you can get help from Audio-gd if required. My correspondence with them was hassle free.
Build Quality
The NFB-12 was superbly packaged - plenty of packaging - and the unit arrived in pristine condition. Overall the unit appears nicely finished with a machined finish on the enclosure. Corners are nicely rounded. On my unit, everything fits nicely with no excessive gaps in the case work. The alps pot is extremely smooth. The connectors on the back seem to be quite high quality. The overall weight of the unit is pleasingly hefty. Inside the unit is very tidy, and well laid out. The unit runs warm to the touch - but so far has never progressed beyond merely "warm". My one compaint would be the lack of decent "feet" on the unit to keep it elevated from the desk. Easily solved with a matched set of 4 foam feet - but something that could easily have been included.
Listening Set-up
While I originally used the USB - very straight forward set-up, I later switched to coax from my mobo. I use Debian Linux, with my principle player being Foobar 2000 run via wine, set-up using wasapi + the SoX resampler upsampling to 24/96. All music is FLAC and is a mixture of redbook and hi-res 24/96. Main listening is done with the HD600 - gain setting on high gain.
Impressions
Out of the box, on the default setting (factory shipped) I found the amp too warm for my liking, and while it was very smooth, lacking top end detail. Bass wasn't overly well defined. To be honest I was a little disappointed at first. I continued listening for about two weeks on the default setting - and while I got used to the overall signature, I still felt it was too warm - and not what I was looking for. So I unscrewed the top plate, and started playing around with the filter settings. Being able to adjust the filters (tailor the sound to your own preferences) is fantastic. After a lot of experimentation, the two settings I found best suited to me were:
4X oversampling , Minimum phase 'soft-knee' filter (MPSKF) - good mix of detail and warmth
8X oversampling , Minimum phase apodising filter (MPAF) - a lot more detail, and tightening of bass as well
One wish is that they had included a selector at the back of the unit to quickly select between different digital filters. This would have been a "killer" feature - and really made this unit stand out against the competition.
The power of this unit is quite astounding. With the HD600s on high gain, the pot is set at about 9 o'clock (ie 25%). Switching to low gain, I can still not turn it up much past 11 o'clock (not even half way).
With no music playing, I tried the pot through to maximum setting - and it is completely black on my unit (no audible hum).
Comparison to E7/E9
(These are from my notes - E7/E9 long since sold). The first thing I noticed comparing the Fiios to the Audio-gd was how spacious and more 'alive' the NFB-12 sounded to my ears. I had previously been very happy with the Fiio combo - and perhaps it was the slightly added warmth of the NFB-12, but the difference was clearly audible and the signature of the NFB-12 very much preferred. Both had extemely good detail (especially with the NFB-12 on the new MPAF filter). The NFB-12 just simply had more body and life - while the Fiios in comparison seemed a little thin.
Comparison to GoVibe PortaTube (an excellent transportable mini-tube amp)
I was surprised by how similar these amps both sound. Both have a delightful warmth through the midrange - while retaining a nice level of clarity. Both have a sense of spaciousness (Mozart's Overture to The Marriage Of Figaro) with the NFB-12 having a slightly warmer and fuller tone - but also conveying a little more overall space in the playback. Switching to a track with plenty of bass (FATM's 'Drumming Song') - both again very similar, with bass impact being very good on both units - and really is a coin toss.
Other Features
I also used the rear outputs to my powered desktop speakers (Creative Gigaworks T20's). I tried both the fixed and variable output settings and both worked well. I eventually just used the fixed setting. Finally - I've also tried the fixed output (NFB-12 as DAC only) to the PortaTube - very clean and clear signal. My aim is eventually to add a desktop tube-amp (thinking Valhalla) - the impression from the NFB-12 > Porta-Tube was very positive.
Summary
For approx USD200 (245 incl shipping to NZ), this has been one of my best purchases to date. While the warm signature may not appeal to a lot of people, I find the combination of warmth and body (while still retaining sufficient detail - for me anyway) to be very pleasing. The build and form factor is great. The DAC seems to be very clean, and quite neutral (via my tests with the P-T), which bodes well for adding a more detailed tube amp at a later date. For an entry level desktop or bedside dac-amp, if you like a warmish signature, I'd highly recommend this as an entry level set-up. I can't think of too many dac/amp combos that have this many features for the price.