Hmmm. Are you a science guy or an "I believe my ears" guy or both?
Are you using the built in Chromecast DAC (Analog 3.5mm out) or Toslink with an External DAC?
Have you seen any measurements that show RF Noise leaking into the signal?
Sorry for all of the questions...but there are a lot of variables here.
There have been some recent CCA measurements by Amir at Audio Science Review of both the
Analog Outputs. and the
Digital Toslink Output.
Recent is good because there have been a lot of firmware improvements since the CCA's release...including implementing bit-perfect transmission (depending on source/software).
Interesting in the Analog Measurements:
.0027% THD + Noise
91.2 dB S/N ratio.
Jitter and Noise 110dB down. So in this test...any RF noise or other power related issues are far below audibility.
These are very very good numbers. Not the equal of the best Dacs...but equal or better than some very expensive ones like the Schiit Yggdrasil.
Note he did not use the stock USB power adapter (he lost it) but used another inexpensive switching power adapter. I have never noticed any 60Hz noise or other distortion on my CCAs using the stock power adapter. I did get some noise when I tried some random other cheap USB P/S.
Interesting in the Digital Measurements:
In the 1st Test of the CCA Toslink outputs the results were TERRIBLE. It turns out the problem was not the CCA at all....but Google's Implementation of Casting Audio from within the Chrome Browser.
When he switch his source to a signal cast by
Roon the results were once again....nearly perfect. Other well designed casting software like Hi-Fi Cast, BubbleUPnP, Media Monkey that use the Chromecast API get similar great results. So the problem is the Chrome Browser Casting function. I wish he would test Spotify Connect Streaming...because I use that most of the time. My guess would be it is as good as spotify direct...which is plenty for me but definitely not Hi-Res.
Another interesting note on the CCA Toslink out is that it has some jitter which really well designed DACS (like the Topping D50) can totally handle. Other less well designed DACS may show some small jitter effects. Rather than purchase a bunch of anti-jitter add ons...it makes sense to choose a DAC with good jitter reduction for use with CCA's toslink. They do not have to be expensive.