Review and Measurements of Audio-gd NFB28.28 DAC and Headphone Amp

[RandomEar]

Hi all,

Since this thread was recently brought back by someone asking whether the Audio GD is still a valid option in 2025, I would like to share my situation and raise a question.

I’ve been using an Audio GD NFB28 since 2014 (as far as I know, it shares the same amp stage as the NFB28.28, but with the older Sabre 9018 DAC). With my Audeze LCD-2 (pre-Fazor) and Sennheiser HD800S, I don’t hear any distortion or noise when using the balanced output, everything sounds clean, neutral, and powerful enough to me. Only when I connect very sensitive headphones to the single-ended jack do I hear a faint hum.

On good amps, you won't hear any hum or noise even when connecting extremely sensitive IEMs. The fact that you don't hear any obvious distortion is not very surprising, as the levels in the review indicate distortion around -50 dB in typical cases, which is just barely below the level of audibility for most people. Test for yourself (but use a different/better amp for the test). It's still a sign of bad engineering in the Audio GD.

After reading the very negative measurements and reviews of Audio GD amplifiers here on ASR, I started wondering if I might be missing something and whether it could be time to try a new amp after more than ten years. I was honestly surprised by how poorly it measured, because my own experience has been very positive in daily listening.

Then I saw that Amir’s review of the NFB28.28 was made through the single-ended headphone output, which is basically a convenience jack, not the main balanced path the amp was designed for (according to the manufacturer). That made me think that perhaps this could explain at least part of the poor measured results, since I’ve always used the balanced XLR output (that would not explain however the poor results of the DAC section, since this was measured using the USB input and the XLR output).

I also noticed that other balanced amps, like the Schiit Jotunheim 2, Topping A90 Discrete, or Violectric V550 (to mention a few I’m also considering), were measured through their balanced headphone outputs.

So I wonder why the NFB28.28 was measured only from its SE output, and whether anyone has ever measured its balanced headphone output. It would be interesting to know how it performs that way, just for the sake of fair comparison.

Balanced is fed by the same signal chain and just gives you double the voltage. There will be no significant difference in the performance - maybe you gain the theoretical 3 dB in SNR, but that's it. The device is badly designed, using another plug does not change that.

More importantly, since I’m considering an upgrade, I’d really appreciate some advice. I’m looking for a headphone amp / preamp that pairs especially well with the HD800S (to give them a bit more body and weight) while also working well with the LCD-2.

I really like the design and engineering philosophy of the Violectric V550, but it may be over my budget if the sound improvement isn’t significant. So I’m also considering other amps like the Topping A90 Discrete or Schiit Jotunheim 2.

Any thoughts or experiences would be very welcome.

Thanks!

If you're open to Chinese manufacturers like Topping, the D90 will perform very well. If you're looking for something else, I would rather recommend amps like the Schiit Midgard or JDS Element IV. Both deliver insane levels of clean power. That's all you could ask from an amp - it should not alter the sound in any way. As mentioned by @Veri , no well designed, correctly working amp will give you "more body" or anything like that. Use EQ or switch to another headphone if you're looking for a different tonality.

 

[easy lee]

Thank you very much for your answers and explanations. Very interesting the JDS Element IV, I'll keep an eye on it.