Running balanced. Difference between XLR vs. RCA.

Would like to know the difference, if any, in running an amplifier, or preamp, in a balanced mode with XLR connectors or running balanced with RCA connectors. Is there any benefitial difference between the two if the runs are kept at 1 meter. I have an amp and preamp that can run balanced with either.
A piece of gear might be internally balanced (or not), but any gear can only offer balanced connection on XLR-terminated, internally-balanced cables (though not all gear offering XLR connectors actually provides balanced output and/or input!). RCA-terminated cables (and I/O jacks) are inherently single-ended in operation, although it's possible that a cable itself may be capable of carrying a true-balanced signal if it was to be reterminated with XLR connectors (not always the case, though - it depends on the cable design). If your gear has true internally-balanced construction (in other words, has duplicate + and - signal paths from input to output), then it will offer true-balanced output and/or input on the XLR jacks, and you would probably be shortchanging the sound not to avail yourself of balanced connection, so try some XLR-terminated, internally-balanced-construction cables. Even at the 1-meter cable length, if you don't automatically get an audible benefit from the balanced cable itself, it is likely that your gear will operate more transparently if you don't feed it a single-ended signal, because it must be internally converted into a balanced signal prior to the balanced circuitry, thereby adding an unecessary active stage to the gear's operation when employing the RCA jacks. BTW, if you plan on doing head-to-head auditions of RCA and XLR versions of the same cable in your system, just make sure to account for the fact that balanced analog connections will usually give a result about 3dB 'hotter' than the single-ended option, thus requiring that you adjust the volume control to achieve matched levels in order to perform fair sonic comparisions - otherwise, the ear will always favor the slightly louder balanced connection, skewing the test.
In my experience it depends on the quality of the interconnect, the system components and your tonal balance preferences. You may perceive a significant difference or almost none at all. I've seen situations where the difference was remarkable, but sometimes only a trade off.

There is no way to know what will work best without some trial and error. It falls into the same category as trying to suggest the "perfect" brand of interconnect, single ended OR balanced.

For example, I auditioned an Audio Research DAC running balanced into an Elliott EASE preamp. I got a much grainer, flat sound stage with generally poorer overall performance than with the single ended. In both trials I used the same brand and quality level interconnects.

In extended testing with the Aesthetix Io phono and Callisto preamp, the results reversed. The same brands of interconnects were used for both tests, with the balanced providing wider bandwidth and greater dynamics over the single ended.

To make matters worse, some components that have XLR connections are not truly balanced circuits. In this case, the extra parts for a balanced connection only add links to the chain without any advantages that a true balanced design might provide.
I've a/b compared XLR v RCA with my SCD-1 to my pre and agree with Albertporters second last paragraph where I too noticed a greater bandwidth and especially better dynamics over the single-ended connections.

However, I disagree with Albert's last paragraph in that I noticed these improvements in my system in which no component I own is truly balanced. Yet I received those same benefits using XLR/balanced outs and ins.

XLR connections typically employ a 2volt increase over single-ended outputs. So the XLR signal is usually 4 volt where the single-ended is usually 2 volt. That additional 2volts can really add a lot of dynamics (live bite) to what could be an otherwise 'boring' presentation.

There is a Catch 22 with balanced cables:

Balanced cables reject external common mode noise, which decreases the chances of that annoying electrical hum;

Balanced cables bond equipment with a ground wire creating another ground path, which increases the chances of that annoying electrical hum.

There are benefits of one to another - both ways. Try each one, the best RCA's and XLR's you can afford. That's the only sure way to answer your question.
My 2 cents... I replaced all my single-ended interconnects with the same brand of balanced, Tara Air-2, and the result was a more musical, less technical presentation. The sound was much more open. I agree that it is system dependent, so the best advice is to try it.
Gs, balanced pro equipment offer a ground lift switch on back to break such ground loops if necessary. Or you can just wire the connector as such.

Also, a balanced input stage in an otherwise un-balanced design will offer all the benifits of balanced input. Why do I people always repeat that? Its just as if there were a transformer input converting a balanced input to single ended, all the common mode is reduced just the same. Is there something else you mean?

I've purchased a pair of Simaudio W-10 mono blocks and P-5 preamp. The manufacturer suggests either interconnects, XLR or RCA, for balanced operation. From the little amount I know of balanced operation... it takes both signals (+ and -) and only amplifies the difference of what is 180 degrees out of phase? Thereby cancelling any added noise? Can it do this with RCA? The manufacturer says if you aren't running in a balanced mode then use only the + input with RCA, and cap the un-used - input, as long as your preamp doesn't invert the signal. If running balanced mode with RCA then use + and -. Of course it does have XLR capabilities also. I contacted Simaudio on this with no recommendations, just some suggested cables. Wanted to get some info from the Audiogoner's experts, and then audition some cables, and let my ears make the final conclusion. Thanks for the responses.
their literature is a little misleading, you will need a balanced xlr cable to us the amp in balanced mode as they are designed for. Just get any cable you like or even a generic pro cable like a Canare or Belden based one and enjoy those amps!

I'm not certain that posts here are directed at my comments about "true balanced." To clarify, pasted below are manufacturers comments that explain the issue I have in mind.

Balanced or TRUE balanced?
"Quite a few high end audio manufacturers have built their amp and preamp circuits around single ended designs (not balanced). When the balanced craze began, they all wanted to jump on the bandwagon, so they did a quick fix to make their single ended circuits balanced. They simply added an extra input (for the 3d wire) which created a balanced input (because it has CMR), but not a balanced circuit.

So, when you hear the term 'true balanced,' it usually means that not only is the input balanced, but so too is the entire circuit."
I recently converted my long time ICs to balanced operation. Other than the increased gain noted above, the sound was the same. IMO, if you have a noise/RF problem, and 'true balanced' equipment,then balanced cables should be explored. Otherwise, relax and enjoy your SE
If SE CKT, using RCA or XLR IC would make difference. But for balanced CKT, XLR will benefit from more gain, CMRR, .... CMRR is more the power supply related, a better power supply will help also. Lower RF noise will help both SE and BL, but not make SE the same as BL.
The only way to find out what sounds better is to try both and use what works best for you as all systems are not alike! Alot will say balanced is better but if your eq. is not true balanced as stated above then balanced may not improve over single end IC. Most systems that are true balanced do sound better with balanced IC, And I mean most systems do but some don't. Happy Listening!
IME, I have either heard no differences with balanced lines (1m) or single-ended sounded better. Now if you are running 10m cables there may be an improvement.
Guys, thanks for your input. I'm going to go ahead and try the XLR's first and see if I like the results. Those W-10's are just amazing. They really brought my speakers to life. I'm on the path to the next level... Yea!
An experience on the question of whether balanced connection can make a difference with shorter cable runs: Between my balanced DAC and balanced preamp, I experimented by trying 1m runs of two different cable types in both balanced XLR and single-ended RCA configurations for each type, and for both types, the balanced XLR examples proved superior (with volume levels compensated to match - the preamp allows for input-level offsets to be pre-programmed to within .1dB for accurate comparisions, which I remotely switched from the listening chair). In particular, running the balanced connection resulted in a presentation that was more dimensionally 'embodied', with fuller tonal saturation and dynamic contrast. These differences were slight but consistent, and musically worthwhile; the effect in balanced mode was unmistakably a bit more believable and engaging overall. So I can confidently say that short run length by itself ought not dissuade anyone from trying out balanced connection, especially with true-balanced components, but as Albert and others have noted above, everything is dependent, and YMMV. You just have to do the audition for yourself...