TOPPING is on a roll off late, having basically mastered the release of ultra-clean and extremely well measuring neutral DACs and amplifiers at various price points, including stacks at the $400-500 price point that realistically do enough for most people. This was always going to be detrimental to anyone making sources though, with the higher priced DACs and amplifiers now struggling to justify their place as features trickle down the product line. The original D90 and A90 stack from TOPPING was no doubt a winner at the time of release, yet I doubt it would have the same positive reception had the release been in 2024. With competition high from others, there's really not much left to do in the so-called neutral source rat race. Sure, TOPPING can add quality of life improvements via features such as parametric EQ, which we see has now come to the D90 III Discrete, but it's also present on the less expensive D50 III too—another recently released DAC from TOPPING—indicating the company does not plan to lock this highly useful feature to more expensive DACs. I can't tell you if the D50 III behaves identically there, but the D90 III Discrete at least offers extensive customization with TOPPING Tune, and allows up to five saved PEQ profiles you can easily change on the go to suit your needs with different headphones/IEMs/speakers alike.

But the real change with the D90 III discrete is the result of TOPPING now going down more adventurous routes. The 1-bit DAC architecture employed in the D90 III Discrete is a big step there, with the upcoming D900 DAC taking this 1-bit DAC approach even further with 32 phases compared to the 16 here—no doubt the D900 is going to be priced even higher. There's even a matching A900 6-channel headphone amplifier coming alongside, in case you wanted to have a big party with everyone on headphones. These are more likely to be targeting studio use though, where having multiple transducers active simultaneously makes more sense to me. TOPPING is even working on R-2R DACs, with the Centaurus already appearing at some shows. It may feel like heresy to a certain audio forum that has long praised TOPPING for its ultra-clean sources, focusing on nothing else, with 1-bit and R-2R DACs typically measuring worse than multi-bit delta-sigma DACs. There's also the part where these custom architectures end up costing more to design and manufacture, as opposed to taking a third-party DAC and having a simpler PCB around it. The D90 III Discrete now costs $999, making it one of the most expensive TOPPING products ever. Yet, in the weird world of 1-bit DACs, especially those which still manage to sound clean and measure really well, this feels like an outright bargain. The D90 III Discrete is not for everyone of course, but those who are set with the transducers and now want to play around with the audio chain will likely find this interesting and more justifiable too.

The TOPPING A90 Discrete amplifier, on the other hand, is a more divided story even if it costs far less than the DAC. The A70 Pro costs $100 less, unless you manage to snag the A90 Discrete from Headphones.com where both are on discount and lower than from others, and offers far more power per channel. If that is the only metric by which you judge amplifiers, as some people do, then surely the A90 Discrete is not the way to go? Yet, I'd argue the real competition comes from the likes of the L70 and A50 series, since the A70 Pro is arguably too powerful to really use with most IEMs and headphones on the market—there's so little useful volume control even on low gain off the single-ended output there. The A90 Discrete is far more reasonable, and in fact is designed such that you get a larger range of power output too, let alone a really nice volume control knob and R-2R volume control system too. I had no issues using it with anything I threw at it, and it does the job really well in that regard. It's just not the best value for money, since ultimately you can get the same experience from a less expensive amplifier too. I wish the A90 Discrete had a display too, and seeing the upcoming D900/A900 stack go for dual displays does make things worse. Overall, this is still a fantastic stack with lots of features—just make sure these are the features you want, and the pricing works for you having considered the alternatives, be it individual DACs and amplifiers or DAC/amp combo units.