Jenne and I did some violin mode damping for ETMY which had some tall peaks at around 510.715 Hz. We looked at the FM2 and FM3 filter and found that they were not at +-60 degree phase. Hence we made some new filters that are actually at +-60 degree phase, and loaded them in the Gaurdian. Also, we detected some old 1kHz filter (from 02), which we deleted. Finally we applied a gain of 0.4 (in steps starting from 0.1), resulting in damping of the excitation which is visible in the change of the peaks (almost by an order of magnitude).
Note that none of these changes are in guardian. We left the old (not actually +/-60 deg) filters in place in ETMY Mode1, so that the guardian will turn on damping for this mode with the previously-good settings, until we have validated that some new settings with the new filters are good.
Separately, it seems a bit as though the best damping settings seem to change as a function of peak height. I accidentally rang this mode up quite a bit earlier today, using positive gain and no phase filters. However, when Rahul and I were looking at it later in the afternoon (after I accidentally rang it up more while trying other settings...), we had good success with no phase filters. Presumably this is due to some confusion with the ~12 mHz higher ETMY Mode6 peak, although it's always hard to tell, since it's hard to have the patience to look at a fine enough spectrum that can distinguish the 2 modes...
Hi Raul, Jenne
Please have a look at my entry from yesterday on this exact issue you are dealing with here, and actually on all violin modes at LHO.
https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=46597