for what it's worth, I don't think I've ever had a Croft amp hiss (unless there was a faulty valve somewhere). they are remarkably quiet, even compared to SS designs (which can hum). I've had limited usable volume knob travel in some combinations, but even with modern DACs I can usually comfortably get to the 3 o'clock notch. & in my experience that was never correlated to any form of hiss. so my vote goes to the people saying there must be a fault in the signal path.