Today I estimated the DAC noise at TM stage as following:

DAC_noise_TM=TF_TM_L2Darm*c

where c is the measured DAC noise value and it is equal to 4.5 e-3 counts/rHz. (see this ref. http://gwwiki.icrr.u-tokyo.ac.jp/JGWwiki/CLIO/Tasks/DigitalControl/Caltech_setup?action=AttachFile&do=get&target=analog_system_investigation.pdf)

The attached plots show the results of this calculation:

-Pic1 shows the calibrated TFs from TM_L to DARM for all TypeA: The TFs show same behavior and can be fitted as 1/f^2.

-Pic2 shows the DAC noise projection measured at IX (yellow line), EY (red line) and the total DAC noise contribution:

According with this plot seems that around 100 Hz we are limited by the ETMs DAC noise.