Nice study, MAB!
I used to own minidsp 2x4hd some time ago and was surprised to hear a lot of hiss in my then active system. I didn't measure, but calculated based on S/N data what the noise was at the output of my power amps and how this translated in SPL from my 86db/2.83V speakers. It's really not difficult. I found that -90db S/N of the 2x4hd is insufficient in active system with high gain amplifiers without volume control.
Taking into account the output noise voltage and comparing it to the SPL at 2.83V of my speakers, then compensating for 2 speakers and the listening distance I came to something about 35db acoustic noise. According to Google that knows everything, this corresponds to the level of "whisper". Whisper is exactly what I was hearing. Quite annoying! I sold the 2x4hd.
My conclusion from all that was that if the volume control is at the front end its minimum S/N should be -110db. Anything else might be audible in not all but some configurations.
Of course, my current E50 + PA5II, having much better S/N than my old system, are dead silent at any volume level. With my ear in the tweeter I couldn't tell if the amp is on or not.
I used to own minidsp 2x4hd some time ago and was surprised to hear a lot of hiss in my then active system. I didn't measure, but calculated based on S/N data what the noise was at the output of my power amps and how this translated in SPL from my 86db/2.83V speakers. It's really not difficult. I found that -90db S/N of the 2x4hd is insufficient in active system with high gain amplifiers without volume control.
Taking into account the output noise voltage and comparing it to the SPL at 2.83V of my speakers, then compensating for 2 speakers and the listening distance I came to something about 35db acoustic noise. According to Google that knows everything, this corresponds to the level of "whisper". Whisper is exactly what I was hearing. Quite annoying! I sold the 2x4hd.
My conclusion from all that was that if the volume control is at the front end its minimum S/N should be -110db. Anything else might be audible in not all but some configurations.
Of course, my current E50 + PA5II, having much better S/N than my old system, are dead silent at any volume level. With my ear in the tweeter I couldn't tell if the amp is on or not.