Why would the digital optical output from my CD player be louder than that of my streamer?

I thought that a digital output audio signal didn't have volume info encoded in it; ie, that the bit depth tells you the dynamic range of recorded sound, from 0 to highest volume, but does not tell the downstream devices how loud the sound should be (ie, what you actually hear, in SPL).  In other words, the volume would be entirely determined by the preamp (after the DAC converts it from digital to analog), not by the digital output source.
But I'm finding that the digital (Toslink) output of my Cambridge CD player is noticeably louder than that of my Bluesound Node, after going thru the same DAC and preamp. Is my assumption of the digital signal having no volume info wrong?

My CD player is louder too. More voltage. Mystery solved.

Not so fast, @hilde45 -- The CD player is sending a digital signal to my DAC/Pre on Optical, and another digital signal to the same DAC/Pre on Coax; for both the volume is the same, but fairly loud.  Now I switch the cables to the Optical and Coax outputs on the Bluesound; again the sound levels are the same, but much less loud. How could higher voltage on the CD player account for that?

Are you streaming a local file that was ripped from the same CD?

I see a few possibilities.

1) The content from your steamer is a different mastering of the same album 

2) the streaming service is adjusting the digital levels as part of their delivery technology. 

3) The bluesound node incorporates a digital volume control and it's not actually bit perfect when the volume is at 100% or set to fixed.