Hiya, so I believe JDS LABS built on their knowledge of O2 to make ATOM(same form factor, same 16VAC external PSU, better measurements) then improved it further with ATOM+ and they are now offering ATOM2 that certainly appears to nail it nicely :
Previously I had the opportunity to try ATOM+ with my Hifiman HE6SEV2 and HE500, it sounded very clear and very uncolored but 1W / channel couldn't quite drive them as Hifiman advises a bare minimum of 2W for HE6SE. But lo and behold ATOM2 is back with 2.65WPC, nicely orchestrated by an army of OPA1656's:
HE6SE is now driven pretty nicely and as the old saying goes "if it sounds bad and measures well it means you're not measuring the right thing", I must say that I really wanted to believe the THX headamp hype but SMSL SP200 was for me a huge disappointment both with HE6SE & HE500 so I then tried MONOLITH 887 but it sounded identical to my ears, like listening from the next room with very poor resolution.
Truth is the whole
THX headamp technology appears to be a based on an opamp that was never meant for audio applications :
OPA564 is general purpose power amp(valve actuator, motor drive) so distortions look on the high side at 0.2% which can be very audible with such sensitive headphones
Surely there are many different kinds of measurable distortions but to my ears on my rig, especially with HE6SE, those THX headamps are vastly outrun by ATOM 2 and its army of audio-grade
OPA1656:
OPA1656 (OPA165x) are BurrBrown™ op amps designed specifically for audio
ATOM 2 really provides great performance to my ears, stereo balance is fine even at low volume, plenty of output power, dual 3.5mm/RCA inputs, trouble-free pop protection, DC protection so your headphone won't fry no matter what, metal enclosure so it stays in place when rolling cables and shields against cellphone interferences, black-painted so it'll become stealth while watching movies in a dark room, linear PSU so it won't throw back a lot of SMPS noise to the rest of the rig and they'll even engrave whatever picture/text you want on the top panel for no additional fee huh:
https://blog.jdslabs.com/2024/03/more-custom-engravings-2024/
I've tried it with several DAC's, they all came with a character of their own(R2R / ES9039 / AK4493S) and every time HE6SE came with nicely textured deep bass, big wide SS and no lack of drive power whatsoever
No balanced output and I know some people claim that HE6SE sounds better with 4 W / channel, but this a small form-factor headamp that costs $129 and for the price there isn't much competition with so many features. Also, most headphones users run dynamic headphones that aren't nearly that demanding and will sound perfectly fine as-is.
Surely I wish they would build a bigger/better/badder version for say $199 but to get a balanced headamp with 4W / channel there usually is a fourfold price increase, mostly because only a niche market would need it so all in all, bang/bucks is very impressive on this nice little headamp that doesn't break the bank and allows to fund better DAC/headphones
As long as the heavy hitters aren't your white whale, it looks like it can drive anything else well. It would be nice if they just went all out and made a competitor to the A70Pro or even the A30Pro or SMSL H300 which I have also.
I still like their support the best. There's some things I've got that would have to be shipped to China if anything goes wrong. I had the Atom+ stack and it was flawless and didn't take up half the desk like the SMSL H400 I've got.