The Duet has a very good black and quiet background with iems (no hiss or noise). Paired with the Solo -dB, there isn't a lot of useable pot movement but it sounds excellent never the less, especially with the Solo and Duet are connected balanced.
It was certainly the best "portable" SQ I've heard. However I put portable in quotes because it's not really portable. Portable to me means being able to pocket it. You're not going to pocket a CL stack.
Does it beat Hugo's SQ as a portable device?