Finally I get some time to check the CK4.
The sound is balanced/neutral and detailed, the music background is really black (! later).
I can feel real atmosphere, the instruments are in right positions, not "in the face".
The bass goes to deep enough without any eq, and dynamic too.
I compared with Musiland Monitor 01 US (in this I made some mod: changed 2pcs elco (to ELNA SILMIC II) and the OPAmp (OP275 -> LM4562))
and it seems to me the difference is not much...
It even can drive the Superlux (56 Ohm), I feel sometimes that the sound maybe a bit weak (not energetic)
but I am sure that will try to get some portable amp in the near future.
I compared to Philips GoGear Vibe SA2VBE08 too, just for fun, and off course "flawless victory" for Colorfly:)
Actually I am quiet impressed with the sound quality of this ~200USD (with fedex shipping to Hungary) device (with one exception!).
The real drawbacks:
- some clicking noise during high resolution playback
like static discharge or playback of vinyl rip
nearly every 10 sec is at least one...and it seems on higher resolution worse)
maybe firmware bug?
I translated with google the C4 firmware release log, and found this: "revised WAV format compatibility issues"
- only wav supported for high resolution playback (>48kHz/16bit) ->
hard to fit in the 8GB+uSD (I have 8GB uSD in my phone, but thinking on 16/32GB too)
There is a need for Flac too.
- no cover art during playback
- user interface, I mean really simple, and the keys at the top with strange order, but I can still use it, and can learn after a while
at least it is responsive and works
- the Line Out can be changed by Volume control
Tested: mp3/flac(44.1/16 48/16 44.1/24 48/24 88.2/24 96/24 192/24)/wav (same)
Not tested: wma/ogg/ape..., video playback (I don't really care about this)
I will continue this...I already tried to contact with the Chinese support for wirmware update (no succes yet).