I got in to an argument with a friend on the preferred connection. I know the tecnical differences between them. But does anyone know of a sonic difference? Hm...

Is there any? If so, why?

Connection for what and where? For short runs of cables, it will not matter much or really at all. People who need to run very long runs of cables usually prefer XLR, assuming of course.....(see below).....

Something to consider is....are you going to pick a piece of gear based on the conections, or on how it sounds?? If you were an XLR person and found a piece of gear you absolutely loved the sound of; would you not buy it because it had RCA's ; and would then go buy something you thought was not as good solely because it had XLR's ??

If some gear you own (or plan to own) has both RCA and XLR connections, I would try it both ways and trust your own ears which your prefer. It is your listening happiness, not your friends..
I´m not searching to buy new gear - settled as is. Me and my friend was just talking about what would be the best termination, as different manufacturers and brands has their ´favorits´ in connections. We have no chance in trying them all ourselves ( xlr, rca, BNC ).

I´m fully aware that it does not matter ´much´. But if I hear a difference between switching brand powerplugs on my PC for example, there should be an audible difference between the chioce on terminations of signalcables.

The ideal thing was if someone had three equal cables with different ends. Xlr, rca or BNC. Had equipment to connect them all and do a simple A - B test. But that´s utopia for an answer.

We can settle for talking the terminations on digital cables, if it helps.
For digital cables the best is non of the above...

ST Glass is probably best (and I don't mean toslink).

Ok, on paper, perhaps. I know they all differ in lab measurements, but if I say in a sonic performence?

Ok, let´s say ST Glass is best ( not ´probably´ best, but best ) for digital.

How about for Analog then?

From the electric point of view there should be no difference, assuming all have clean contacts. BNC and XLR lock in place, so they won't get pulled out by mistake if you move stuff around. XLR are big and clunky, which makes them easy to handle.
I'm not sure there is a "best" termination. I like XLR for my present equipment because it sounds better than RCA. I don't know why, it just does. If RCA sounded better I'd use that.
rca bnc the same to me in digital app. rca verses xlr is a differ like on amp ,pre, and so on.xlr good for long run of wire.they are two diff monsters as in connection app.xlr locks bnc locks,wbt rca locks .you should have a talk with your friends about why they cost so much.like does a 1500.oo rca cable sound better than a 99.00 xlr cable..lol
Of course only the XLR can be used for balanced lines, and balanced XLR should not be compared with unbalanced RCA. By the way, there is no reason why XLR could not be used single ended. There are also "phone plugs" of various sizes that can be either single ended or balanced. And this is just what is common here in the USA. My CarverPro amp provides for something called a "Euro" connector.
I think XLR are best for longer cable run due to less noise due to cancelation. However, for shorter runs, say 1M or less, I think it depends on whether the "from" and "to" components contain fully balanced circuitry. Usually these are higher end, and more expensive since it requires double the parts, due to L+, L-, R+ and R-, e.g. Krell, Levinson preamps, etc. Most components convert balanced to single ended as the first step in the input stage, so If your runs are short, it shouldn't matter.

I believe this can go on for a while. And I see a lot of the arguments me and my friend where having.

The thing is that a/most RCA does an electric ´bump´ as it transfers the signal. The BNC does not, or at least has a lesser ´bump´, according to some cable companies. BNC is therefore classed as a ´better´ connection. But less practical. ( Do not know if XLR does the bump ).

We all agree on XLR´s ability on noise-reduction for longer runs.

RCA or BNC then? What to be prefered?

Any thoughts?
Rannagarden...NO! We do NOT agree that XLR connectors reduce noise. BALANCED INTERFACES are more noise resistant than unbalanced, so IF you have a problem with noise pickup (and this should only occur with runs of 50 ft or more such as are common in Pro sound applications) a balanced interface would be preferred. The balanced interface can be implemented with other types of connectors as well as XLR.

Clue me in...what is an electric bump? Do they grind also?
While you have done well to keep this thread on base, so to speak, it reminds me of the often askes question:

"Other than that one thing, Mrs. Lincoln, How was the play?"

The point being that there are far too many more variables than the base of the connection. For instance, my McIntosh 2102 amp has both balanced (XLR) and unbalanced (RCA) inputs which would be good to use in your test, except that this amp has an extra circuit that converts the balanced to unbalanced so naturally I should use the RCA first as this is my amp's preferance.

My Audio Aero Capitole Cd player works best with my Audio Aero Capitole amp using the balanced connections. So, I use the CD player's RCA outputs to the McIntosh and XLR to the Capitole.

I shall let others get started on quality of cables, kind of metal in the cables, shielding, etc.

This is not to say that your 'bump' is not unimportant, just a bit esoteric.

Ok. Bad choice of words. What I meant was the same as you describe.

´Electric bump´. Thought it was a simple way to picture a difficult thing.
If measured in Oscilloscope cables and any measured signal path will leave a trace in the shape of ´waves´ on the Oscilloscope monitor. A ´bump´ is the same thing as a wave. Ideal is no wave or bump. The fingerprint wave/bump of RCA and BNC differs. To BNCs favor.

I´m not interrested in cables quality, brands or shielding. I know that many will say that one can not disregard all the other things - one must see the whole picture etc. But I´m only interrested in that tiny bit that has the job of connect our cables to the equipment.

Unclejeff - You may be right...