I now have the CH L10 true dual mono preamp (4 box version) that has replaced my CH L1 true dual mono preamp (4 boxes) paired with my CH M1.1 mono block amps running in active biamplification mode powering my biamplified Rockport Arrakis speakers. Just a few comments on what I have read on this thread.
I do have the grounding switch on the L10's set to linked which ties signal ground and earth ground together (as I did on the L1's using the supplied jumper). I also use the L10 in no global feedback mode (local feedback only). I do prefer the no global feedback setting on the L10 as it provides a more involving and organic musical presentation (this is with the M1.1's set to zero global feedback as well). After about three weeks of break in on the L10's, my CH dealer visited me and we did some further listening evaluations. First we wanted to see the effect of adding some global feedback using the M1.1 feedback setting which allows adding global feedback in 10% increments. And since I run the M1.1 amps in active bi-amplification mode we only added the feedback to the bass drivers of the Arrakis speakers and left the global feedback at 0% for the tweeters, mid range and mid bass drivers. Over the course of three days, we compared 0%, 10% and 20% feedback on the bass drivers and each time we tried this, we both preferred the 10% global feedback setting on the M1.1 mono's for the bass drivers. Images were more right sized, bass was even more textured and the overall sound was just more natural to us. I look forward to hopefully hearing the M10 mono's later this year where the global feedback adjustment can be done in 1% increments.
As for grounding, one of the changes that CH has also made is adding a dedicated earth ground input (via banana connection) on the L10 power supply which did not exist on the X1 power supply used with the L1. I use a CAD Ground Control Reference (GCR) grounding box for my front end components and with the L1's, I connected the signal grounds of the 2 L1 boxes to the CAD GCR. I also started this way with the 2 L10's. With my dealer here, we compared grounding with the signal grounds of the L10's to the earth ground of the L10 power supply. We both felt that using the earth grounds of the 2 L10 power supplies was even more effective than using the signal grounds of the L10's. It improved the sound in similiar ways, just more so.