Is it worth upgrading a CD player?

You can always improve your musical reproduction, but the question would be why.  If you are happy with the music then leave things alone, because real solid improvement means examining all components from power to speakers and determining the best order to replace components and that can be the start of a major outflow of cash.  I started thinking that I would just do one thing and then I realized that I wasted my money without another upgrade and so it went for the last eight or nine months. Don't start if you are happy where you are.

@jerryg123

If playing a CD has better sound qualityr or streaming is better is completely dependent on your equipment. On my equipment Red Book CD is eclipsed by HR streaming and equaled by streaming of Red Book CD format. In fact on average streaming equals my very good vinyl leg.

Which is my point. If you are going to work on a particular source… streaming is the one to pursue… the cost / benefit of having top notch streaming just completely eclipses buying and owning CDs.

I have given away my 2,000 CDs. They serve no purpose after a couple years of just collecting dust.

@carlsbad 

Streamers Have extremely low bit rate requirements and most cashe the data. My streamers work flawlessly when I cannot get my news page to refresh on my iPad. Clearly a DAC is important, but like everything else in high quality audio, sound quality is hindered by your weakest link. I have streamed using, iPods, iPhones, PCs, MACs, iPads and about half a dozen dedicated streamers (and also DACs)… and the streamer really maters! Like every other component.

@facten

I’d suggest ignoring any advice that suggests that the transport doesn’t matter, that bits are bits, yada , yada, yada

I agree with your entire post and particularly this wise advice.
OP if you’re really happy with your current situation and sound quality, leave it alone. If you are determined to extract more from your CD listening experience, that is definitely possible. Just depends on what you are ultimately trying to accomplish.

As facten said, ignore the “bits is bits” mindset. A dedicated high quality CD transport will very positively impact your listening experience. DAC quality matters , and so does transport quality. A mediocre CD /digital source is only going to mitigate what a good DAC is capable of providing. Better CD transport means better DAC performance. This comprises your digital front end. They work in harmony as a pair, not in isolation from one another.

Inevitably all topics concerning CD playback will have the streaming alternative thrown in. Just the way it is now. That’s your call obviously. I believe that nearly everyone at this point is aware of the existence of streaming. However, there are plenty of listeners who prefer physical media and spinning CDs. Strange as that may be. So strictly a preference issue. 

Charles

I have an Oppo 105 which I've enjoyed for years. Highly regarded and lauded. Then Iauded a Schiit Gungnir DAC, making the Oppo a transport and the sound just bloomed! 

Your Marantz first was produced in 2007, 15 years ago. You could probably stand to invest in a more modern CD transport - the California Audio Labs Tercet Mk 3 comes to mind and then experiment with DACs.