So.... Connected to the Xonar I hear a very faint static noise. Connected to the motherboard, I don't hear any distortion... Ultrasone pro 900s, which I believe are not very sensitive.
However with the Asgard connected to the motherboard's jack, I can hear the noise... Is it the Asgard then, I would be surprised...
The PRO900 are relatively sensitive (about on-par with the RS-1) (data: http://www.innerfidelity.com/images/UltrasonePRO900.pdf).
When you mention a "static noise" from the Xonar, is this similar to white noise or hiss? If so, it's likely just that the Xonar's gain is too high or some other mismatch with the fairly sensitive and low Z Ultrasones. Does this noise go away if you hook the Asgard up there and the Ultrasones to that? (I know it probably creates another noise) That'd be the easy way to confirm (or use the Mamba in this capacity).
Is the noise similar to this:
http://www.youtube.com/watch?v=1KaOrSuWZeM (this is kind of loud, so don't crank the volume - note that it does fade in so the initial volume is quieter than the volume 10 or 20 or 40 minutes into it (ALSO: who on EARTH would listen to this? I love that I could find this so easily, but come on, TWELVE HOURS?)). If so, that's not a "problem" with the Xonar, it's just a mismatch between the Ultrasone and the Xonar - you can get an adapter to kill that (we'll get to that). You may also just try lowering the gain setting on the Xonar (if possible) and seeing if the noise goes away there.
At this point my thinking:
- Something is wrong with the Asgard, either internally, or it's silly 3-pin wiring causing a nice loop with the PC.
- Something *may* be wrong with the Mamba as well, or it's ability to source clean power from the PC. If it has an external power supply, or you have such a power supply (if you have a modern mobile phone it probably has a 5V USB power supply) I would test that out to confirm this (if it still misbehaves or misbehaves running on its battery, then something is wrong, if it only does it drawing from USB power off the PC, that's just between the PC and it, and you basically work around that).
Luckily, the Ultrasones don't require an amplifier that can move heaven and earth to drive them, so you can get away from the Asgard with no negative side-effects. I would continue troubleshooting the Mamba but otherwise I think the issue lies with the amplifier.
If any of the above is redundant to what you've already done, I apologize - I'm working on what I can assimilate and piece together from what you tell me, so I'm "behind" the curve and may be repeating myself or suggesting you try something you've already done. If that's the case, just ignore those steps or report back what happened if it was interesting (e.g. "I tried the Mamba on its battery only, and Darth Vader came down from Planet Vulcan and told me he'd melt my brain if I didn't ask Lorianne to the Enchantment Under The Sea Dance").
