Sorry for my ignorance.
How are the S400NC using NCore or the S400ET using Purifi different? Is one or the other objectively better in some way? Eg, lower distortion, better dynamics, less heat etc.
If you want to dig into info, here are the datasheets:
NC400 datasheet
1ET400A datasheet
The Purifi Eigentakt module certainly objectively beats the NCore on distortion, by a fair margin. But the NCore's already so good there, it's questionable the improvement is human perceptible, not least because speaker and room distortion is way higher.
The Eigentakt wins significantly on idle losses - 1.7W compared to 4.5W, and is slightly better on overall efficiency, so will produce less heat.
Power handling is similar for both, so dynamics should be broadly the same, although the NC400 supports higher current so would be more appropriate for really-low impedance speakers. For 4 ohm or above, they're both suitable. (The new Purifi 1ET7040SA addresses the low-impedance domain, at the cost of some distortion and efficiency).
Both were to a large extent designed by the same person - Bruno Putzeys - and the Purifi is the next generation of his efforts.
To be honest, I think most of us who have chosen Eigentakt over NCore are guilty of just wanting the latest and greatest. I would not want to put money on me being able to tell the difference audibly.
Edit: Oh, and here's Amir's tests+review of a non-Audiophonics NC400-based amp, to compare to this one. But all NC400-based amps should perform broadly the same.
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