Is there a difference in sound quality when streaming TIDAL Vs CD player


I hard wired my modem located in my family room using Cad6 cable to my Apple TV and direct wired my Apple TV to my ARCAM AVR550.  I have an OPPO 203 connected by both an RCA cable and by HDMI to my ARCAM.  

The dealer I purchased my ARCAM from told me to play my CD’s through my RCA connection and to watch DVD’s through HDMI.  If I listen to CD’s through the RCA, aren’t I using the DAC on the OPPO player rather than the DAC on my ARCAM and wouldn’t the DAC on my ARCAM be a better DAC.  My friend told me I should use a digital cable rather than an RCA to improve sound quality to utilize the DAC on my ARCAM?  If this is the case, wouldn’t the HDMI be the same as by using a specific digital cable?  I listened to my CD’s through the RCA Vs the RCA cable and I thought it sounded better through my HDMI cable.

i will be looking forward to your responses.

Thank you,
128x128larry5729
The Oppo DAC is adequate, but to get the most out of your digital sources, you need a stand-alone DAC. Mine is an Aqua La Scala, not cheap but well worth it.
Agreed, it’s all about the DAC. When I say DAC I refer to the DAC/opamp device that takes the digital signal and convert it to a usable analog signal, not the individual chip. This device might be stand alone or imbeded in a larger piece of equipment. Having done trials on many DACs I find it is very much an individual thing. A DAC is like a musical instrument, different DACs have distinctly different sounds, so the Best DAC device is the one your ear prefers. In my case since I’m older and my HF hearing isn’t as good as it once was, I prefer a DAC that is designed with high resolution and timbre that others might find bright.
Just a side note. Many people are unaware of the fact that TIDAL offers a discount to Active Duty and Retired Military and Veterans. Since I'm retired Navy I get my TIDAL HiFi for $11.99 a month. 
I didn't realize a DAC can make such a SIGNIFICANT improvement in sound quality.  Can you really hear this difference with a blind test?

I have a difficult time believing you can hear a significant difference in speaker cable and interconnects.  

I think if I had a choice between spending $5,000 on expensive wire, I would benefit a great deal more if I purchased a new pair of speakers that cost $5,000 more than the ones I purchased.