RCA to XLR adapter, advantages of special boxes ??

Agree with the posters who point out the difference not just in the connectors, but between the S/PDIF (RCA) and AES/EBU (XLR) signals. One of the best ways you could accomodate this connection, IMO, is to buy a new or used Monarchy Audio DIP jitter-reduction box (these are a steal at about $250 new, and sometimes less than half that used, with the latest and supposedly best version being designated "24/96", but any of the iterations should work fine). It will accept Toslink or RCA S/PDIF inputs, and output a cleaned-up and reclocked balanced AES/EBU signal on XLR. In addition to its very effective jitter reduction properties, it is also features transformer-coupling on both its digital inputs and outputs, electrically isolating your converter from your transport's or computer's ground-plane noise.

WOW, discussion became hot ! I really appreciate your help.
Question: if I shall invest some money, for that Monarchy box, wouldn't be better to invest it in a new CD player with AES/EBU output ??
Which prices ??
I could sell my actual one (DPA Enlightnement) that has already 5 years of operation !
What do you think about ??
Which budget should I afford for a decent cd player?It might be that 500 USD will beat already my DPA, isn'T ??

It's not my intention to send you off on an expensive upgrading spree or anything, but my experience FWIW has been that a better transport will always make an audible improvement over a lesser one, no matter what is used following it in the chain, and that conversely the DIP will still continue to improve on a good thing, even an upgraded transport. Many audiophiles have reported that when it comes to jitter-reduction, more is better (of course, many audiophiles have also gone back to one-box players with the latest models, even at the high end of the market).

To answer a particular question of yours, yes, going balanced out of the transport directly into the DAC will usually be better than going single-ended directly, all other things being equal, but no, going balanced and direct out of the transport will not necessarily be better than going single-ended to a jitter-box and then balanced to the DAC. But you must weigh that statement against the very real possibility that dollar-for-dollar, you might in your present situation get more for your money by just buying a better transport with an XLR output on it to begin with, since your CDP both lacks this output *and* could probably be improved upon as a pure transport vs. a dedicated component - remember, nothing that comes after the transport can improve upon whatever information isn't recovered at the source.

So if I were to rank the elements preceeding your DAC in descending order of precedence, I would say #1 transport, #2 digital interconnect, and #3 jitter-box (with power conditioning, AC cords, and even physical supports being important all around as well). But I can't comment on your specific player though, as I'm totally unfamiliar with it, and all of this speculation assumes you'll be happiest keeping the DAC you have as well, something I'm also unfamiliar with. So please don't take what I say as anything more than just the very general opinion of one guy, and keep in mind that digital component and cable matching issues tend to be very system-interdependent and subject to personal preference.