Opus 21

Does the Opus 21 invert phase or is it non inverting?
I don't think it does.

However, to make sure, I suggest you contact Jeff Kalt, at Resolution Audio. (A nicer, more helpful guy, you will never find!!!) Here is his number.

1 (415) 553-4100

Or email him at: info@resolutionaudio (dot) com

Good Luck!