I just got my iDSD today. First impressions... It doesn't work with my Linux Mint Nadia and it doesn't work with my N900 H-E-N. I wish there was a fix for these problems... Anyways it works perfectly under Win 8. I hope it will also work well under Win 7 in my office, but that I will see on Monday. Anyways, that all about me disappointed. Let's now get to the good things about iDSD.
I tried it with Momentums, and built-in headphone amp did the job very well, Momentums sounded better than ever before, i.e. definitely more detailed. I wasn't actually expecting these cans to be capable of presentation of such an amount of detail. Tried Alpha Dogs next. iDSD drives them well, but I could turn volume to 100% without getting deaf. Still it was quite loud, that I wouldn't normally listen at such volume, so I don't know whether it's good or bad... But, since I love complicating things I connected iDSD via RCA's to Pan Am. I have also replaced tubes to brand new NOS matched Mullards, and then connected Alpha Dogs. I have also connected digital output to my NAD T744. I started by listening to some Nightwish, then some ASOT by Armin, and now I'm listening to my dearly beloved "Tron Legacy: Reconfigured". The sound is coming at the same time from headphones and from loudspeakers that are powered by NAD. I matched the volumes, so when I take off headphones I head same sound at same volume. Note, that sound that goes to NAD as far as I understand skips iDSD's DAC. So I have comparison between how DAC in my NAD sounds on QA 2050i vs. DAC in iDSD though Pan Am on Alpha Dogs. I would say they sound very much the same, with slightly more detail on Alpha Dogs, but both signatures are very close. So, the NAD has very big, very heavy, and very efficient power supply built-in, while iDSD runs from battery. This small and not very expensive DAC in my opinion performs as good as DAC in this heavy NAD. At the beginning I was afraid it would sound too digital, but the longer I listen to it I start thinking it's very musical. It is a pleasure to listen to it, at least though Pan Am as amp.
Good job iFi! If you could only look at these issues in Linux, I would be more happy