Well, they have an international shipping refund coupon going on right now at Drop.
Thank you! I used to do a lot of reviews, but I’m about 6 years rusty, so I’m glad I still covered important stuff and gave a good impression.
Do you mean the Monoprice Liquid Spark DAC, or the amp? Because the Spark amp is a bit of a different product than the DAC. I have no idea what the character is of the DAC, but the amp has a more romantic musical sound (not a dry, analytical, shouty sound). In some ways, it’s one of the more “tubey” sounding solid state amps, so if you didn’t hear a difference between it and the FiiO, then maybe either your headphone is coloring the sound so much that you can’t hear the difference anyway, and it’s also true that some of these changes are less obvious and harder to observe when you don’t know what to listen for (not always evident in all songs). Like a sommelier can better distinguish the tastes between wine, an experienced listener can more quickly get a feeling for differences. Most amps are not like equalizers that change the frequency response of headphones… it’s more like how they blur and sharpen sounds, don’t sag and sound anemic in the bass, handle dynamic volume peaks in the music recording, crosstalk, have pleasing/unpleasant distortion in more/less quantity.
I do own an E10k, but I haven’t used it in about 6-7 years, it was OK but didn’t leave a distinct character in my memory (I’d have to listen again to get a better idea). The coolest thing about the E10K is that it can act as a DDC and convert USB to Coax if you have a coax-only DAC (which is literally the reason why I bought one, I had an old Theta DAC).
If you’re happy with the e10k sound, but you just need more power, the Air CAN – uh – can do that. But the Liquid Spark could have done that too, as it has a massive power output (like the specified 1300 mW into a 50 Ω load is a conservative estimate…), and most headphones don’t need a ton of power (check a headphone power calculator tool and fill in your headphone’s specs).
If what you’re actually looking for is a difference, because you want to have fun (which… we’re listening to music, watching movies, playing games, having fun is certainly a fine goal!), then messing with the xBass and xSpace features of the Air CAN do give you an A/B comparison and I feel they’re fun to mess around with.
The literature around the S-Bal output is indeed confusing. I’m not even sure the description of S-Bal is consistent across all of iFi’s products 
. It seems like sometimes it’s got a power amp each for the right and left channel, other times it’s just a single power amp and they’re doing something special with the grounding. I read iFi’s PDF that explains S-Bal, and even with the diagrams it’s still not entirely clear to me how it’s wired! The PDF document states that the Pro iCan and three other older amps mentioned can accept a balanced plug with four connection points (Chinese 3.5Pro TRRS plug), but there’s no 3.5mm TRRS output on the ZEN Air CAN. Well, 4.4mm Pentaconn uses four connection points (technically it’s also TRRS), so maybe that counts… but I briefly read something from an ex iFi engineer who created S-Bal who stated that the new designs aren’t the same as what he designed.
If we take them at their word though, apparently on the Air CAN the end result and user benefit is that it reduces crosstalk without the typical noise increase of balanced amplification, aaaand essentially the 4.4mm output is simply adapted from this “reduced crosstalk” unbalanced circuit. So, yes, the power output is the same on both connectors, and both the 6.5mm and 4.4mm Pentaconn outputs have reduced noise and crosstalk vs a typical unbalanced connector.
Another thing that used to always mess me up was with their iDSD products: they expect you to turn the iDSD on first, THEN plug in the USB cables, but I didn’t know that so I kept thinking my iDSD Micro was defective. The Zen products were thankfully simpler to use.
