Hi Raul,
Thanks for the many recommendations. I'll add them to my list in case I decide to upgrade phono stage and/or preamp someday.
The phono stage was a Sonic Frontiers, an SF-1 I think though I never saw or heard it. It had both an MC and an MM phono stage. It was boosting a Shelter 501MkII (.4mv) into a c-j PV-10 preamp. The owner tried the following configurations:
A. 501 >> SF-1 MC input >> PV-10 line input
B. 501 >> BentAudio Mu >> SF-1 MM input >> PV-10 line input
C. 501 >> BentAudio Mu >> PV-10 MM input
He reported that A was the worst, B was much better, C was best. We can ignore C for this discussion since it merely compares the two different MM phono stages. The comparison of interest was A vs. B, where B was reportedly much better.
The SF-1 had three adjustable gain settings: 44, 54 and 62db. I presume (hope) the 62db setting was being used for configuration A and the 44db setting for configuration B. That would put A and B just 2db apart when my 1:10 SUT's were plugged in. Any thoughts?