This isn't a new topic, but it's pretty new for me. I've been using an Ayre QB9 DAC for years and am very happy with it. The only problem is the hanfshake between my Innuos Server and the DAC, there isn't one. Can't explain it but turning on the Server doesn't switch the DAC out of standby. I've had to unplug and reinsert the USB cable for two years, to do that, very annoying.
Yes I know a powered USB gadget might work, but it's another link in the circuit to mess up the sound. Well. I've been looking for a new DAC and had more or less settled on a Chord Qutest, but looking around online, I came across Metrum, the Octave DAC in particular. It was hard to find any criticism at all, very simple, just plug it in and play. The Mark 1 version has no USB input and the Mark 2 only has USB as an optional extra. No headphone output, no volume control, no display, no digital filters to obsess about, just plug in and play. Over in Europe it's available for around $500 second hand.
The Octave is just wonderful. is it better than the QB9, no just different. Comments on NOS DACs have suggested they are smooth, lacking in dynamics and detail. Not so, this DAC is fast, has good base and detail and yes, it is Analogue Like. An abused term, but the DAC sounds like a good vinyl rig or tuner. Listening to an old favourite "Silver Lining" by Bonnie Raitt last night, you can hear deep into the musicianship of her great backing players, the rise and decay of each note.
The moral of this story? If you're thinking of a new DAC, perhaps try and listen to at least one NOS DAC and no, I can't give a list of DACs using that topology. Perhaps try Metrum's current crop of DACs