I am amazed how well this works. Some stepped relay implementations lose their grip at low volumes but there we go past our limits of hearing before the mismatch even registers!

Topping A90 Discrete Listening Tests
I have been using my everyday Dan Clark Stealth headphone as a “it won’t drive it but let’s see what it does” test for headphone amps. This is the first time I have seen an amplifier have such an upper hand over these headphones. The sound is incredibly dynamic and beautiful. “Loud” listening is at volume level 80 in high gain. I cranked it up to 95 before I got scared for my hearing without any hint of distortion. I had not heard these headphones come to life so well.

Needless to say, driving Sennheiser HD650 and Drop Ether CX was in a walk in the park. I am talking incredible bass, detail and fidelity with volume indicator in 60s.

What a joy….

Conclusions
I must confess that I got a bit worried when Topping told me about the A90 Discrete. I worried that they were making a discrete version just to appease audiophiles but with much loss in noise and distortion metrics. Happily Topping approaches everything with extreme focus on performance and they managed to get the A90 discrete within a split hair of the op-amp version. But then innovated with stepped ladder volume control, trigger support and major step up in class/look of the unit. I happily take these as a trade off for that 1 dB of SINAD.

From design point of view, this is another watershed audio/engineering event brought to us by Topping. Who would have thought that this company would keep breaking new ground instead of all the major/usual names we know in hi-fi.

It is my pleasure to add Topping A90 Discrete headphone amplifier/pre-amplifier to my recommended list. My challenge is to figure out if it goes in my main system or desktop!