I purchased the new NFB 7 with the Amanero Combo 384 USB in September of this year and have been listening to it every day since delivery. My comments are as follows:
Software;
A annoying but inconsequential problem with the NFB 7 and my prior NFB 27 is that occasionally and for no apparent reason, they would stop working. Cycling the power on the DAC solves the problem. I am a Mac user and this has occurred since 2012 (NFB 27) on various laptops and operating systems. The current setup is a 2014 Mac Mini, El Capitan via JRiver 21 to the DAC via USB, I have also used the Sonore Rendu Via SP/dif BNC with the same results. The bulk of my music is 44/16
Sound;
I have had 4 Audio GD DAC since 2011 and (WM, 1704 and ES) and while they each had their particular flavor, the "house" sound of neutrality is maintained. Though this is neither good nor bad, I always found something was missing to include the current model. To be clear, the DAC is highly resolving over the entire audio range, has realistic attack and does a good (not great) job with soundstage and instrument separation but seemed to lack "air" and always caused a mild tension in the back of my head and shoulders. This is all slightly improved via the BNC and Rendu or CD transport but not transformed.
I have had the Audiophileo AP1 and Pure Power for sometime (update by Phil in 2013) and plugged it in just as a "might as well"... Transformed. The DAC is so good in every respect including major improvements in soundstage, instrument/voice separation and it now has that elusive "air" that was always missing. Most importantly the tension in my head and shoulders immediately subsided in an almost erie "now its gone" sensation. Without delving into the religious wars surrounding which and why USB converters work, it just did. So I sent the unit (AP1 only) back to Phil for and update to his latest MkII S offering. With the MKII in the system, a slight improvement in noise floor can be discerned though there was no apparent noise floor issue before. I have not tested any of the AP1 features or functions other than as configured by Phil nor have I played with cables etc.
It would seem that Kingwa's mastery of this chip can never really be appreciated until (pick your flavor) a converter is implemented which is irritating, but the end result alleviates all consternation.
December 21:
I did some testing today with different cables and connection options on the AP1/Pure Power. After testing options 1 and 2 from the PP manual the following emerged the clear winner on the current system (2014 Mac Mini 16GB RAM, AP1/PP - NFB 7 - Audiopax Model 5 - First Watt SIT2/F2J - 100dB 15 inch Co-Axial in A8 cabs). Audioquest Diamond USB direct to Ap1 from the Mini with a $1.95 USB to the PP. I did also try a 2.5 meter BNC SP/dif but came back to the supplied double BNC with the AP1. This combination had the cleanest, clearest sound with maximum extension at both ends and the most accurate timbre. When transposing the cables, the timber fell off noticeably. The NFB 7 now is virtually absent from the equation adding or subtracting nothing, truly dead neutral. It also is much less ruthless with poorly recorded venue and there is not even the slightest hint of harshness, glare or glaze.
December 31:
Today I swapped a 2013 Audial Model S (NOS 1541a, 2 BNC input and 2 RCA out) into the same setup as mentioned above with the AP1/PP to compare it to the NFB 7. I have always preferred the sound of the NOS DAC and have had various incarnations over the past 10 years. The Audial had been in the system prior to the NFB 7 for at least 6 months so I was familiar with its presentation. The NFB with the AP1/PP trounced the Audial with the same setup. The NFB, as mentioned before is essentially not there, it sounds like music. The Audial sounded good but midrange centric (no surprise there) and most revealing of all, like recorded media. While this is certainly not a scientific evaluation, the difference was so apparent, no squinting was required.