I have an old school Sony Receiver (Sony STR-DE985), hard wired to some mediocre speakers (Bose 201s with subs and front/rear channels). The last few years it has sat in storage while I used a Harmon-Kardon SB-26 at work on my Windows PC. Now that I’ve retired I recently started putting all of my music together (almost a TB) and discovered ROON.
I’ve got a unused PC with fast processor/lots of ram/storage and optical outputs. I’ve installed ROON on that and it sounds decent (to my very untrained ear) running through the soundbar but I hate to have the larger better sounding speakers sitting idle. What I have been thinking about doing is running an optical cable from the PC to the receiver to use the speakers. But after reading several articles on here about modern DACs, would it make more sense to run the cables to a DAC and then the DAC to the receiver? I considered the Cambridge Audio Magic200 but it only appears to have optical inputs no outputs, how much quality would I lose running regular phono jacks? Or, is there a better solution, I’ve got a budget of about 1K USD to work with and am open to try something new (except headphones).
I would first buy a small (used) USB DAC, e.g. an AudioQuest DragonFly Red, and plug it into the PC. From there, connect a mini-jack cable to a free RCA-in on your receiver and then see how far that gets you. If you find joy in Roon, you can always make bigger updates later.
Just one possible solution. Most important: enjoy the music. 
Cheers
Uli
I tend to agree with @UliR, start small and see if this works for you. Two modestly priced DACs that have a USB input for a PC and an optical output for a TOSLINK connection are the Topping D10 series and the Emotiva Big Ego+. For these or other options, connect your PC USB port to the DAC and then connect an optical cable from the DAC to the Sony receiver.
Every DAC has its pros and cons. In this case, the Emotiva has a more limited analog output, but I use mine only for USB-to-optical conversion. My Topping is also used in a similar manner, but has a better analog output capability. I’m sure there are others also, but best to try it first on a more limited budget if possible to see if this works for you.
Very good idea from @Robert_F with the TOSLINK option.
Later you might want to set up the PC separately from the receiver and connect a streaming transport in between, the whole thing then running via ethernet. Then there are many more possibilities, but once you start, you’ll want to do more… Be warned…
I’ll consider myself warned, thanks for the response.
I will check both of those out. Thank you.
Using a DAC upstream of a multichannel AVR makes little sense. Surround processing and subwoofer bass management operate on digital audio.
AJ
I don’t understand. From everything I’ve read the older electronics have DAC really capable of decoding most modern music. If fact, almost every article states that the DAC is 70% of what you really need, which is why I’ve been told my sound card in my PC is so inferior. I figure about the only thing the older AV is good for is wattage to the multiple speakers? Have I misunderstood this completely?
I think most A/V receivers from the past 10 years or so have perfectly fine DACs in them. And the DAC isn’t 70%. The speakers are 80%, the source 10%, a perfectly linear amp 5%, and the DAC maybe the other 5%.
“Almost every article…” Unfortunately, most of what is available to be read in hi-fi magazines and websites and fora is marketing from the advertisers who just want to sell you gear, not tell you the truth.
My advice would be to just run the optical cable to the receiver, and see what you think. That receiver does have an analog “pure direct” mode, so you’re probably not totally wasting your time with an external DAC, but the better thing to do would be to improve your speakers. They matter most.
If you do go with an external DAC, know that there’s no need to spend a lot of money. Perfectly good cheap DACs from the likes of Topping and SMSL are available.
Bill
Thanks for the advice. You’re correct, I did get most of the material from YouTube Advertisers and “experts,” ( I know, I know), and from a place called Moon Audio. On the bright side they convinced me to use Roon, instead of the Plex system I was using. I will probably throw the Cambridge Audio 200 magic DAC in, I just picked one up for $200 on eBay, that should work.
I think this is excellent advice.
Sorry, but why would you connect an optical cable (=digital signal) from your DAC (=Digital to Analog Converter) to your receiver.
You probably mean connect RCA out (L + R analog cable) from the DAC to the receiver.
If you don’t want/need an additional DAC in your chain, then what about an RPi + an S/PDIF HAT, such as the HifiBerry Digi2 Pro?
Use RoPieee on the RPi, and then you have a networked Roon Endpoint that will feed digital audio to your STR-DE985 using either an optical or coax cable.
Well, now you can have fun trying to decide whether it sounds better than the built-in DAC in the AVR. Enjoy!
Connecting a TOSLINK output cable from a DAC to a receiver’s optical input keeps the signal chain all digital and allows the receiver to perform the digital to analog conversion and any signal processing locally within the receiver.
The DACMagic is simply loaded with inputs ?
It has 2 x coax, 2 x optical, USB and even Bluetooth
Then either balanced or unbalanced outputs
It also has a headphone output $200 was a bargain
I was under the impression that using fiber optic cable on the run (about 20 feet) would introduce less noise/loss on the line, than using copper cable. Am I mistaken?
True, but you have to look at specs for toslink if can handle 20feet
Why do I suspect now would be a good time to visit the otolaryngologist for a hearing test. 
How far is the PC to DAC,
Or Does your amp have balanced inputs , they are suitable for long runs
Roon architecture recommend a PC then Ethernet to a streamer eg Raspberry pi then to the DAC say by USB
it sounds like a geography question