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
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.
Larry
You should hear a difference between DACs in a blind test. Interconnect cables usually can make a describable difference, however, I don't think spending $5K on speaker wire will be worth it. I use $100 worth of 10 gage stranded and twisted pair by a company called KnuKoncepts (available on amazon)  on my Maggies with great success. I've compared it to cables costing 10 times as much with no apparent difference. The 10 g prevents any voltage drop from the amp to the speakers so there is no loss of power. 10g is about as big as one can have and still make a direct connection to an amp or speaker. I've seen some very high end wire by various companies that look like fire hoses, but I think that's mostly a feel good experience as the connectors become the limitation. The stranded and twisted aspect is most important. Electrons don't travel down the center of a wire, however they travel down the surface. The stranded wire increases the surface area for the electrons to travel making a stranded wire a clearer "highway" for the electrons to travel. This assures that the impedance of the wire does not vary much thru the frequency spectrum. Twisting the wire cancels noise effects caused by nearby radio frequency devices. 
Well, I’ve taken the road in between. I purchase ICs, A/C and speaker cables that sell for $300 to $900 from the manufacturer GroverHuffman.com (as a beta tester, I auditioned 100s of cables from his and other companies).

I would rather $5,000 on speakers too. However. for about $500, one can purchase excellent high end speaker cables and pay $4,500 for the speakers. Also, one can purchase really high end speakers used for $5,000. For only $2,500 or less, a pair of Legacy Focus or even less for Legacy Signature IIIs, easily driven by low watt, high current receivers and get high quality sound.

I hate the term blind listening test for audio.  Some other nomenclature should be available for an audio test of equipment, cables and tweaks.