" higher quality control in the A30" lol, did you even look at topping review on amazon?? Topping has a ALOT of poor reviews for products, some very poor reviews. Secondly value wise Not looking at a massdrop 02, but a mayflower.; im not sure which one has more power, i think the A30 does by a good bit, to serve a niche of very power hungry headphone's, which is cool if it doesn't break, like so many do, and i think massdrop only offers 30 day coverage.., but one thing that's nice is that the 02 has a 10 year warranty out of mayflower electronics, I think the topping has a 1 year warranty from select stores, value? The 02 has a battery, so you can use it as a portable, mobile or desktop amp, and the big argument is the 02 has a nice low output impedance, so it can be used with much more headphones, with the A30, you buy it, then you most likely just need to buy another amp later for "normal impedance" headphones, unless of course you have multiple amps., because the A30 doesn't properly drive normal-impedance-headphones.., Normal being the norm, 32ohms., becuse it's lowest resistance output is 10ohms, The 02 takes care of everything very well to utpo a very high power requirements, and then you need something specialized for high impedance headphones like the A30., then i THINK the A has an advantage fort taking care of hungrier headphones.,.., but these alone are big value differences, 10 year warranty, more uses, low output impedance support for common consumer headphones, i'd say is ways more useful and more value for most people than having more power on tap for VERY HUNGRY headphones, which are rare, but if thats what you need then it's not contest, you have a certain power requirement to fill where the 02 won't work,.., but i think for MOST PEOPLE thats a MUCH smaller value compared to low impedance headphone support the 02 has, and 02 gets way better customer satisfaction.,, To top it off. i think they both offer about the same performance roughly, when they both support the same headphone.., Remember, the 02's SNR is rated to 105db@400mv , however I believe it's 115 a-weighted and 112db@1vrms, and a 130db dynamic range at full power. The A30 doesn't list at what voltage and application it's rated at for it's 126snr, for all we know the 02 could top it at that voltage and application too, or it could be @ 400mv (doubt it),. the voltage setting could make alot of difference, but they dont tell. i mean, the way i look at it is, with the A30, you get high unreliability but the possibility of supporting some uncommon applications really well (and that is only high-impedance-headphones headphones, if 80ohms is the beginning of high, i think, if you consider 8 as low impedance headphones, and 150 as moderately high, and 300 as high, and 600 as very high, since 32is normal for modern "consumer" headphones), otherwise your stuck with the high impedance output and need a new amp, on the other hand, with the Mayflower 02, you've got much greater reliability in warranty, and satisfaction reports, and you can power all typical headphones very well, low impedance headphones to high impedance headphones, so long as it's not too power hungry., now, technically the claim of the A30 being maybe better, with the 126db claim, again we don't know the settings, and even if it were technically superior,, which i think is very well possible.., not that it's a bad choice, to consider; but that i suggest even pending; in many cases there will stil be no difference still, i suspect, since the noise floor is way down and similar, and the dynamic range of a cd is around 96db, and probably most dvds far below 110, and tidal im sure well below, so if your listening to that source material, i think the end performance will be about the same and the A30 will just limit you in the most common employments of an amp, low impedance(eims, balanced armatures) and moderate impedance headphones (moderate being 32-48 (shures's, 32ohm spec, ect), and probably most new headphones to come out in the future, and not only this, but the battery means you an use it for alot more application with those headphones, on a belt-clip to phone or Bluetooth receiver/dac, or on a plane, on a jog, in your bed, whereas me, i wouldn't move a stationary amp round too much i'd probably buy multiple amps for different stations., with the 02 though, because it's mobile; it's like you CAN cover alot of applications without any trouble., want to occasionally play retro games bring it to your Atari, nintendo, or commodore hardware? 02's got you covered. wanna listen to your audio on the go without dynamic range compression of virtual volume controls? line out your mobile to the 02 and enjoy quality support on the go, Got high impedance output to normal headphones from a common pc soundcard? 02' solves the problem.,., Watch to output your tv receiver or bl;uray player occasionally ()where you might not want to buy a stationay amp for occasional use?) no problem, 02's go your temporarily covered. Need more juice for some moderately power hungry cans? 02's got you covered. Got any 5 headphones which arn't super power hungry,. 02's got it covered. Need to power moderately power-hungry high impedance headphones? 02's go you covered. Need to power power-hungry hungry headphones which are high impedance? A30's got you covered. Need to power high impedance headphones? A30's got you covered. Willing to gamble for possibly better performance for high impedance headphones? A30's the mystery! But a moderate impedance headphones' better with the 02, due to the output impedance, generally speaking BY FAR. It's actually an "in spec" implementation. Now, if the A30 is performing better at a common application (headphone they both drive without being power compromised..) thats kind of a serious deal, especially perhaps with some really great headphones and some really quality audio source, but were just inferring this from a put up number, since measurements and real specs and real numbers have been withheld by topping so far as i seen. 126 what, a-weighted? allegedly? Notice how they only list the output impedance of the nx4s? Wonder why that is? We'll i'm sure they know the figure is "undesirable", for harshly limiting applications. I haven't seen the two amps compared properly, verbosely, with given measurements and whatnot at various settings; so it's hard for me to say which one is actually preferable at a common demonstrator. the a30 could be a moderate step up in cross compatible applications, not sure, but were not sure, what we do know is that the 02 covers way more applications, but that might not serve someone as well with a high impedance power-hungry headphone collection. So put simply, i think these amps for for two different applications just even in headphones, 1(02): General headphones barring high power requirements. 2(A30): High-impedance only headphones, and high-impedance power hungry headphones. I mean, that's my take away. Also, 02 is made in the usa for 100 bucks with a 10 year warranty, A30 is made in china for 100 bucks with a 1 year warranty. You wanna say the topping with all it's complaints is a better value, i don't think i could say that, at least until we see the A30 clean the floor with the 02 with a common denominator, and even then, i think that will probably be only for rare cases and mabe not even an end result., One think i do think we know, is that the A30 has more power on tap for high-power-requirement headphones., to speak in laymans terms., So however, this uncommon application of the a30 effectively lowers the overall general value i think, except for those with certain cases. Topping hints that the A30 is superior at a common application, however withholds specs, 02 by the designer lists specs in fairly robustly, but still a touch lacking i think, especially by stores like massdrop mayflower, ect., I feel listing the uncommon 400mw snr rating at 105snr certainly hurts 02 sales, as compared to the commonly compared to 1vrms rating, other amps are now rated at, which i believe is 112 or 115 for the 02.