The CV-591/URR is my favorite of the add-on product detectors manufactured for any application. It just works well. I have found it to be a perfect match for the R-390A/URR.
The unit is a result of the magic that Rick Mish does. This unit was a bottom up restoration. After the Rick Mish restoration it looks and works immaculately. In this picture the CV-591 is mounted in a
cabinet with a small speaker panel. All was painted black to match the R-390A/URR.