So some new thoughts on the Vali, sound and microphonics.
Microphonics - they go away completely if left fully untouched for some time (4-5 minutes), once warmed up. The whine is non-stop for the first 10-15 minutes after turning on, and doesn't really depend on touching the unit or not. This is without any music playing. I test this with the HD650 and an IEM, using the H650 and playing music, I'd say 60 seconds is enough.
Once the unit is really warmed up, I can even turn the volume control without ringing if being very careful. If it starts to ring slightly, 30 seconds and it's gone. Using the laptop on the table, moving things and generally working causes some ringing, but not very loud. My unit needs to be isolated on a different surface. Typing next to /touching the unit causes ringing, but once warm it's not that bad and fades quickly.
Using the IEMs, it eventually goes completely silent in terms of the ringing, but the noise in the amp sounds like water running in the background. To me it's a no-go for iems or even my vmoda M80.
Comparing to the O2 amp, using an ODAC as source, I find that it has thicker tone and the bass lingers longer. Detail is at the same level, cant really tell any big difference in soundstaging or imaging. I like the added impact/thickness that's added, when changing amps I find that I want to turn up the O2 to get the same bass response. Overall the midrange feels thicker.
Please note that I've got no way of level matching the units, and even short term memory is a fickle thing... For the tone differences, as Harman Kardon's "How to listen" illustrates, characteristics are often not based in the frequency range you guess.