while this NX3S looks like an interesting product, i looked it up awhile ago online, but found that the output impedance is 5ohms, (unless "2 people" lied to me or were somehow mistaken) which I feel, sadly makes it unsuitable for general system implementation, since it's out of spec for most headphones for achieving a good damping factor.. Certainly worse then a modern creative Soundcards 1ohm output impedance or a FiiO A5... Like, it's a shame they have that figure, otherwise I'd probably be in., Also, as an Nx5 owner, Also, i think the build quality of topping offerings isnt nearly to the same level as a FiiO like A5., there are reports especially on the flagship NX5 model, if you go to amazon japan, (where topping is more sold than amazon America) you'll find lots of complaints about the NX5 headphone jack and USB jacks shorting, with mild use.,, not saying that effects all their models, but effects their top shelf models, and I'd trade my NX5 for an A5, just knowing this. They have more low star reviews where i seen on the amazon page of certified purchases, they have more 1 and 2 star reviews than 5 star reviews.,, And that's a red flag for me.. The FiiO A5 has reinforcements made to the TRS jacks, to suspend them in-place mechanically, to prevent the failure of electrical connections made by mechanical stresses, while the NX5 has reportedly insufficient mechanical enforcement to protect the electrical connections, and that all mechanical enforcement of those common jacks might actually just be the electrical connection.., which i say is largely a concerning thing., Which is one reason i think the A5 has a much better build quality then the less popular Topping offerings. That said, the NX3s is a newer product than the NX5, so those design issues maybe have been addressed, or might not surface here. I personally inquired about the NX3s's output impedance, and was reported by a retailer to be 5ohms, now the person trying to sell it to me might be lying, however, it makes sense given the output impedance's of their other products, like the nx1s being 3.5+ohms and the Topping A30 desktop amp being 10ohms and 30ohms output.. Good for certain headphones maybe, but limited implementation certainly I'd say. The Benchmark DAC company says aim for a 20 damping factor if possible, to ensure an unknown implementation should be well, so I'm not sure i could vest myself here unless i was looking to support a very specific headphone.., it would suck to buy the device, and then buy a new headphone but then need another amp/., Generally I'd rather loose a bit of SNR to gain that flexibility in implementation.. Certainly cant properly pair this with sensitive low impedance iems eh, But certainly i'd think it should be good for a number of headphones =) Just saying, it would suck to buy this amp, and then 3 months later need to shop again an almost identical one but for a low impedance headphone. this is one reason i differed from the NX3s so far.. not even talking about the money so much as the hassle and the money., lol The second being concerned about topping builds compared with say the competition; FiiO. That said i read one person say the Topping portable amp flagship NX5 has an output impedance us below 1ohm, but i read elsewhere it was 8ohm, I have not the tools atm, or time to measure, but i think i'll be pairing it with a 250ohm headphone for a single application anyhow.., just food for thought fellow people, on the nx3s. You might not realize, it doesn't have an under 1 ohm output impedance, it's 5 shopper. At least, thats what was told to me, Topping only advertises the output impedance of the NX4s, which is below 1ohm, but imo; actively hides the figures for their other offerings., is this who you want to give money to and support? Where is it specified here on massdrop?! I don't think it's responsible as a consumer, in that sense to give money to a company(topping) which seeks to mislead consumers.. They should be listing even their challenging specs, so that a consumer can make a sound choice, and not try to make every sale and hoodwink those uninformed into a possibly poor implementation., but serving goods which to deliver strong results. i duno if you can support a company which deos that. Also, i read the nx5 has no overcharge safety off,.. so is a fire hazard., I'm not making this up, i'm just the messenger as a witness for my fellow. The nx5 is a few year older product i think, however.