I posted this in the Asian/Chinese threa but though it would be natural to post here as well.
Since yesterday I've spent all the time I've manged to compare my new Cayin C5 with Topping NX-1 and FiiO E12.
I must say that I find it really difficult to compare and not the least describe the differences. I 've got really big respect for peolpe able to make full comparsion between different aps. I'm just going to give a short comparsion between the C5 and the other two.
Let me first underline that all differences are really small and it took a lot of listening to be able to find them but they're deinitely there.
I used th LO on my X3 as a source and splitted the signal to both amps. I also volumed match by my ears only. Headphones used was my modded T50RP (BMF DBV3 mod with HM5 velour pads), AKG Q701 and Grado SR325is with HM5 velour pads. IEM's used was Hvai B3Pro 1 (original), my most hard to drive IEM's and Logitech UE600, my most sensetive IEM's.
C5 vs E12: Both of these amps packs enough power to drive every headphone I own. I've been using the E12 a lot since I got it about 5 monts ago as I tend to listen less and less out of my desktop amps because of me listening at different places around my houset (with four childre I need to find places I can enjoy them music without getting disturbed or disturbing others).
I've been very pleased with the E12 for the time I've used it. I only paid $88 for it shipped, brand new so I consider it great value. The two main differences between the two (and these differences are very easy to hear) is that the E12 is warmer and has more background noice (hiss). This is naturally worst with the UE600 but it's actully noticable with all HP/IEM's I've tried with. This has never bothered me before but in comparsion with the C5 it's very obvious. The C5 has a very very light hiss with the UE600 and noting with the rest. The warmer sound on the E12 makes it feel a tad less clear and neutral.
C5 vs NX-1: These are actually much closer in their over all signature than the E12 and C5. It took a lot more listening to be able to find the differences here. I've seen one graph on each of these and there they're both really flat. The most obvious differences here are also the bakbround noice (hiss) that's clearly noticable on the NX-1 and as mentoned above next too non-existing with the C5. I've also get some EMI interference from my phone with the NX-1 that I was not able to reprocuce with the C5 for the half hour or so I tried them together. I would also say that the C5 is a tad fuller sounding without feeling warm or unnatural in any way. In a way I'd guess one could say that the C5 is a NX-1 on steroids, having a very similar over all sound but packing a lot more power. With the T50RP's (my hardest to drive headphones) the NX-1 sometimes feels a little bit looser in the bass than the C5.
Other differences between the C5 and the other two may be "new toy syndrom", placebo or not carefully enough mathed volume levels but I do feel that the C5 is a tad more distinct and "right" sounding.
In short I would describe the C5 as being natural, have a really nice black backgound and plenty of power (even the Havi's get enough volume at volume level 3 out of 10 on low gain). It's a great amp and I'm really happy with my purchase.