Does the streamer effect sound quality

I’ve had the blue sound, the Lumin, the Cambridge, the overall advice is that it’s hard to logically separate what these devices do. If it’s only to transport bits into a DAC, or to provide a processed signal, and does it attenuate volume? One of these three will give clues as to what may cause audible differences. My bet is in that pesky volume knob. I ended up with a crazy expensive preamp just because that volume knob seemed to make a huge difference. I’m thrilled with the Apple TV to control the music and deliver bits to the dac and then preamp has the volume knob. If a product can handle all three it’s great but all I’ve listed didn’t tick the box in my listening. 

@ghdprentice  The TOSLINK optical link was specifically designed for 2-channel audio for CD quality bandwidth.  The interface components at either end are of mature design, not a "throw in" item of questionable design. Optical cables are immune to EMI/RFI and ground loop problems. Optical can have jitter on the order of a few nano-seconds.  Any decent DAC will easily deal with that. 

SPDIF can suffer EMI/RFI and ground loop issues. A clock signal is embedded that has to be recovered.  Potential jitter is data dependent and there are low pass and high pass filtering effects to deal with.

Properly implemented either TOSLINK or SPDIF is more than adequate for high quality serious audio.    

I went from the very good Bluesound Vault 2i  to an Aurender N200 and it was a huge difference.     Great machine. 

But CDs sound better than any high end streamer right?  Assuming the same DAC.

I'm not so sure about that.   There is a lot of 24/96 and higher material out there.   The other night I was playing Pete Yorn's 2003 The Day I Forgot on vinyl.   It sounded really good.   Just for S&G I played the same album on Qobuz and it sounded pretty damn good.     It told me one thing , I need a better cartridge......