audio lag with DAC

IMO your issue has nothing to do with the Sonos Connect especially since you say it started when you introduced the 2nd DAC. The DAC would be my guess as the cause.

The next question is are you experiencing the lag when trying to send audio captured by the CXN100 to Sonos via the Connect; or does it occur when going direct to your Amp?

If trying to sync Sonos speakers (using the Connect) with speakers connected to your AMP that will also be a challenge.

One more point...don’t assume that everyone knows what a CXN100 is. Rather than having someone like myself (who doesn’t own every piece of audio equipment manufactured in the world) have to research what a CXN100 is...just tell us in your post that it’s a Cambridge Audio Streamer. 😊

Modern DACs shouldn’t be adding a lag.  DAC technology is 50+ years old, and the math goes back 100+ years, so the chips are basically commoditized.  If your DAC is adding a delay, it is either not working correctly, or it is an affectation by the manufacturer to make it seem it is working harder than it really is. 

Does this help, ‘Short Delay’ setting on filter?

https://www.whathifi.com/reviews/cambridge-audio-dacmagic-200m#:~:text=The%20Cambridge%E2%80%99s%20three%20digital%20filters%20%E2%80%93%20Fast%2C%20Slow%20and%20Short%20Delay%20%E2%80%93%20offer%20fairly%20subtle%20differences%2C%20albeit%20some%20level%20of%20sonic%20customisation.%20We%20find%20ourselves%20settling%20for%20Short%20Delay%20%E2%80%93%20it%20seems%20the%20more%20punctual%20of%20the%20three%20in%20relation%20to%20timing%20%E2%80%93%20but%20it%E2%80%99s%20worth%20experimenting%20with%20them.

The Cambridge’s three digital filters – Fast, Slow and Short Delay – offer fairly subtle differences, albeit some level of sonic customisation. We find ourselves settling for Short Delay – it seems the more punctual of the three in relation to timing – but it’s worth experimenting with them.

 Your connection path description confused me.  You have the CXN & the Connect separately connected to the DAC Magic… Right??

I was also puzzling over this aspect.  The Connect and the CXN100 are both streamers.  Why two?  What are their distinct roles in your setup?

 Maybe the OP wants to access servers with the CXN.  Allows for larger library access.  Also the CXN would not be limited to 24/48.  It’s possible the Connect is for whole house audio.  Just a guess of course.