RCA to XLR adapter, advantages of special boxes ??

Dear All i need to connect my CD player to a DAC converter. Doing this i would need an adapter S/PDIF coaxial RCA(CD)/ XLR(DAC input).
What's the advantage of boxes like the one below ??
Can't believe that such an higher expenditure does not bring any better music result, isn't ??
If the box is useless, could you give me a good adapter cable producer that will make the sound thrilling without pulling my legs ?? (range 50-70 USD for a pair)
I don't know what claims are made for the box that your link leads to, but if all you need is an adaptor Purist Audio manufactures one that retails for $75.00.

The other option would be a RCA to XLR digital link such as (again) Purist Venustus, retail at $425.00. Probably less that the adaptor boxes you ask about.
There are several solutions besides the box you refer to. The advantage of the box is that there are so many options. Whether the box itself degrades the signal via poor connections, soldering, or switches would be a question I might be concerned with. There are more simple adapters that simply adapt RCA to XLR. The better ones are made by Neutrik and often come with BAT components (I think BAT markets the Neutrik adapters under their name). You can also find cheaper adapters at the local Radio Shack or electronics supply store. I don't know if these are identical to the BAT/Neutrik adapters, but they are only $10.49 each on this site, which is a world away from the BAT price, and they are made by Neutrik:
You can also find some cable makers that will make, and do market adapter cables with RCA on one end and XLR on the other. Stealth Audio is one, and I use their CWS (cross-wrapped-silver) cables to go from my single-ended CD player to the direct input on my LS2B. Excellent cables, but would cost at least double your budget. They do come up used on Audiogon but still tend to go for more than $140 a pair. The adapters would be the cheapest solution. Remember XLR come in both male and female so make sure you get the right one for your application. I believe you'd loose the advantage of grounding that the XLR to XLR connection would otherwise provide if you are going from (or to) single ended. Someone correct me here if I'm wrong.

Good luck!
Your signal from the CDP is a single-ended signal. In order to get a differential signal for the AES/EBU specification, you need two signals, one non-inverted and one inverted. The box that you speak of generates these two differential signals from a single digital signal. The differential signal will give you more noise immunity and probably less jitter as well.
I want to thank you all 3 guys that helpend with good advises. Few more info as a feedback for your courtesy:
the DA converter is a professional one used in recording studios, this is the reason it has XLR plugs.(believe me much better that hi-pricey DAC often sold at hi-end)
Unfortunately, but with a future upgrade this could be improved, my CD player has only two possible output:
S/PDIF coaxial RCA or Toslink lightpipe. This is why I need to take the single ended from the CD and plug it into the DA converter.

At the same time the DA converter has XLR output and as usual my preamplifier has a simple RCA input !

Yes, JAX2 I realized I will lost the balanced advantages, but as said, with a future upgrade..........

Tks to anybody so far
The kind of adapter differs from regular analog RCA-to-XLR adapter because S/PDIF & AES/EBU have different communication protocols. The DAC won't recognize the S/PDIF protocol riding on AES/EBU connector if you use analog RCA-to-XLR from BAT or Cardas.
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.