Yesterday we modified the notch fitler to face the reintroduction of noise at the WE violin modes frequencies. In order to improve the response we relaxed the Q ratio of the pole/sero structures. (fig.1,2)

The results was to loose an amount of phase at the DARM HF line frequency (491 Hz), see fig.3, and at the UGF of DARM (fig.4).

The results didn't affect the performance of the loop itself, but as a drowback this morning we had to retune the monitor of the DCP, which is based the loop for the alignment of SR.