NFB-3: 2x PCM5102 chips
NFB-2.32: 2x WM8741 chips
NFB-17.32: 2x WM8741 chips, balanced output
Compared to the more expensive Audio GD DACs, these use a higher number of SMDs (surface mount devices), which reduce size and manufacturing cost by mounting components directly onto PCBs.
However, some think the older through hole construction (components with wire leads that are soldered onto the PCB) DACs sound better.
The NFB 3.32, 3.33 and 17.32 feature SMD components. The NFB2.32 does not - through-hole all the way!