I'm pressuming from your response above here that there has to be a "down-covnversion" or some sort of compression of the original SACD source material (transmitted via HDMI/Coax digital) to a lesser rez output, when processing these EQ circuits?First, I was talking about HDMI in which case there is conversion to PCM but no compression or loss in the process.
Second, you cannot get SACD via coax/digital at all.
And in the case of analog connections, as you said, a digital to analog to digital to analog conversion chain?Yes. Many believe that the advantages of room EQ entirely justify those additional conversion, if they are done well. This is something that can be easily tested with a bypass switch and only you can determine if a particular A/D-EQ-D/A device is transparent enough for you.
I think what you are missing is that there is no compromise (loss of purity) in converting SACD to PCM, imho, and that the advantages of room EQ are so significant that they would outweigh any compromise, if such existed. In fact, the conversion is done (and almost always necessary) even to effect bass management, interchannel level and interchannel delay setups.
You should go out and hear these things rather than prejudging them from the opinions of others (including mine) or from archaic presumptions.
Kal