DDC? For what.? Digital to Digital converter? These were introduced as a band-aid when DACs had horribly implemented USB inputs to overcome bad cables, noisy PC ports, ground loops, and using the PC clock in synchronous mode. Those issues were identified and solved long ago. You can buy entry level DACs immune to these issues. As in sub $100! No excuse for an audiophile level product to be susceptible to these problems just as it is no excuse for a streamer to be susceptible to any phantom network problems any more.
Now, if your DAC does not have a USB input and that is all your PC has, then you need a "media converter" to convert USB to PCM or TOSLINK. Or a DAC that does, PC that does etc.
Chuck, I have heard good things about the Geselli DACs and they have been most responsive with a couple of questions. I do love small companies who believe in service and support. One reviewer suggested their use of a third party USB card may not be the best but that is the only criticism I have seen and only from one source and I don;t believe most reviewers anyway. They just introduced the newest version with the top AKM chip. Roll your OP amps if you wish. Very tempted.
Yea the RME has a book for instructions as they give you about all possible options. As they are a pro audio company, they do their one consumer produce like their pro stuff and expect the effort to be put in. Not for everybody. Better than Chi-Fi that have lots of options ( most useless) but no instructions. Incorrect settings can defiantly degrade the sound. RME and Chord do discuss the digital filter clipping problem but if using a PC, it can be corrected on the host reliving the DAC of that problem. So what was an advantage 6 years ago, may not be today.
The other side of the coin are folks like Schiit, JDS, Geselli, etc. who select " the correct filter" by their experience and can do standard formats without drivers or settings. Plug and play for WASAPI, but drivers are needed for ASIO or ultra high data rates MS does not support. No idea about Apple or Linux. I had issues with older Topping and SMSL ASIO drivers as well. They seem to have worked it out now. Schiit still does not seem to like ASIO. Then a few, usually higher end, give you only a couple of options, but ones that actually matter. OS or NOS for instance.
Giant killers may be a fallacy. You don't get something if you don't pay for it. BUT, Just because you pay for it does not mean you get anything more. Billet aluminum, glass displays, fancy feet, and advertising does not effect the sound. Good engineering does. Dealer markup and very low production also raises the price with no sonic benefits. Overseas shipping can add to the cost if single units. Technology does play a part as R2R with any accuracy is very expensive. Paralleling multiple top line D/S chips does cost. So does licensing for useless features like MQA. Now, how many price steps does one need to go and actually get solid performance improvements? How far above the best budget ( JDS in my view stomps the Chi-Fi bottom tier) does it take to get a noticeable sonic improvement? Different for sure can get you into low end R2R under a grand. Better is or not a personal choice. Features, like if you want XLR's costs a couple bucks. Preamp section or headphone section? Adds up. A $200 mass produced Chi-Fi with top 10 level classic measurements does not sound any better to me than my Atom+, Nor did a $400. So that pretty much confirms once measurements are better than the .001% range they are not the driving force in the sound. So a baseline of pretty good.
Now what does it take to be a real sonic step up?
Pontus, HOLO, Weiss, Chord seem to be a reasonable expectation to be an actual step up if one can believe any reviewer. I don't but are a place to start listening for yourself. Others of course. Above their price, from my manufacturing background, there is not really much you can spend money on, so price may be more prestige driven. Maybe the J2s is the intermediate step but then I have to add the price of a preamp to it. $300, $700, $1500? Maybe add in a higher current cleaner power supply? I hate headphones so that cost is defrayed but it does make it a $1000 minimum DAC in my system. 5X my all in one Chi-Fi which is not bad. Only slightly below, and that may be my imagination of my $200 Atom stack. Imagination. Out brains lie like a dog. I at least know I have a slight bias against the Chi-Fi stuff.