i gauge my tolerance for hiss based on whether i detect during music - my speaker rig has floor noise that is just below that point (Pioneer M22 + Lowther Alerion). the R10 is picking up a level of hiss above that point and once it physically distracts me with music running, it's a non-starter. i'm particularly sensitive to this for one reason or another. probably spoiled by my last two solid state amps (GS-X Mini and now the Naim) which are as close to pure black noise floor as i've ever heard.
thank you! that's been one i've thought about a few different times, not just for R10 but also Utopia.