Well, what I can do is relate to you my impressions of both stacks as I hear them and what I enjoy. I don't know where you stand as far as the measurement game goes or how important that is to you, but if this is something you care about the Topping stack wins in that regard. Although measurements may play some kind of role in improving sound quality, I am not sold on the fact that insane measurements equates to better sound. After all, many people love the sound quality tubes bring and we all know how they measure. So in the end, go for whatever brings you the most enjoyment for your music. Comparing the stacks, I would say the Schitt stack is superior (IMO) because of the multibit sound which I am a proponent of, to me the music just sounds more substantial and real whereas the D90, while being a very good DAC just sounds drier and less engaging to me. The A90 is a very good transparent amp that doesn't impart any coloration of its own and allows the DAC to shine through. Regardless of what many will tell you, a DAC isn't just a DAC IMO. It is a device that creates music! It is taking those ones and zeros and recreating the original analog signal from them. I am no engineer, but the more accurate the recreation of that signal the better the sound will be. Both DACS do this in different ways and I'll leave it up to you to which technology you prefer, but to me multibit is where it's at hence why I much prefer the Bifrost 2. The Jotunheim 2 I have had for a few days now and I prefer that to the A90 because it is a discrete amp, not chip based, has gobs of power that powers my Arya's, HD600's and Elex the way they were meant to be. It maximizes the attributes of my headphones. It also has a better soundstage and ever so slightly on the warm side of neutral which imparts a richness to the music that I very much enjoy. The A90 powered them for sure, but didn't maxmize the headphones the way the Jotunheim 2 does. The bottom line is, Schitt maximizes their gear for the best sound quality at their spcific price points and Topping is maximizing their gear for the best measurements with sound quality being a secondary consideration. Not saying the Topping doesnt sound good because it does, but just not as good as my Schitt gear. These are just my 2cents and ymmv. Hope this helps. Also, I am not into MQA or DSD or any ultra hi-res 768k stuff, give me a well mastered recording on redbook audio and I am golden. My CD's from the 80's, for the large part, sound much better than the new stuff these days due in large part to differing mastering ideologies, IMO.
