I just had to read this message to convince me to buy it:
Here is another message talking about the S1:
https://www.head-fi.org/threads/obscure-chinese-daps.720512/page-294#post-14032647
I have spoken personally with
@deltecdpa about the F.Audio players and he says that even the Xunsound XS01 has better sound quality than the S1. It also costs twice as much. The problem is that the XS01 plays some background clicks, which are played with certain types of music.
Why people don't speak about this awesome player (F.Audio S1)? I don't know, it may be that your DAC does not draw attention to the DAC used by the Zishan Z2 / Z3. But what does that matter when it finally sounds better, is better built and its battery life is more long?
Z2/Z3 comes with LM4562NA opamp. LM4562HA is the same but with another capsule, called TO-99. This kind of chip can dissipate more heat and this seems to affect the final sound quality. I do not distinguish differences between them.
In my country (Spain) LME49720HA it's discontinued. The store offered me the LM4562HA and told me it was the same model, or current replacement model.
Technically who should buy or manufacture a player whose output impedance is 100 Ohms? S1 has 9.3 Ohms, it's also high for use with low impedance headphones. The rule for a DAP not to change the frequency response of a headphones is that its output impedance must be 8 times less than that of the headphones.
You can read more here about "
Headphone & Amp Impedance":
http://nwavguy.blogspot.com.es/2011/02/headphone-amp-impedance.html
I think that the great benefit of Zishan is its volume control, its unusual aesthetics, and the possibility of altering its sound by changing components.
For me S1 is better than AGPTek Rocker, its sound is narrow in comparison. Ruizu A50 HD and Rocker have a similar sound, I prefer the A50. But S1 is in another league. Agptek H1 is a DAP that I like a lot, it has a very nice warm sound. I have not compared them face to face because I prefer to have the H1 in a good memory. S1 has another profile, it is clear, brighter.
Definitely and without a doubt S1 is the best DAP that I have below 60€.
Finally I wrote a review of the Z3 in Spanish in this blog:
https://auricular.org/zishan-z3-reproductor-mp3/