I was deciding between the SU-9 and the M400 and I ended up getting the SU-9, which is actually at $400. My wife pointed out the mistake to me earlier to day.
Quite the opposite. It's called competition. ASR didn't do its favor by measuring at 4V instead of the full output voltage which gives extra 2dB performance boost.
You can think whatever you want. But don't just be judgemental because you could assume something out of seemingly evidence. Competition between SMSL and Topping has been happening since about a decade ago. If you want to continue, you can go ahead. Everyone else around here already got a clear picture.
Thats exactly the point. I never paid attention to that figure while searching for an amp, but now it is becoming essential and key (OTOH I might have soon 130,5 dB instead of "only" 130dB and my DAC ranks first on ASR tables where 120 dB is the end of the hearing threshold, .... happy!!!).
It is very difficult to find an amplifier who's input impedance is below 10k; the vast majority have input impedances far above this. The manufacturers don't state this spec because its always high enough so the amp is unlikely to load any upstream component you're likely to use with it. Its simply a non-issue in the real world.
Could you tell me specifically what is being sacrificed by the passive output? 1,200 ohms is not all that high an output impedance, and as a designer myself for a relatively large audio manufacturer, I see and use buildout resistors all the time on the output of line stages; it is standard practice. Generally its done so that muting relays can short the output during bootup so pops and other noise don't manifest themselves, but its also done for other reasons. All that is taking place in this DAC is that they are using the IV stage (itself a high quality opamp) as the 'output stage' and combining the tasks of buildout resistors and filtering together. A rather smart move I would say. If I were designing a DAC for my own use, this is the way I would handle the output.
