I always did and still do, only to a point, believe that the main reason to choose XLRs over RCAs is to reduce noise, when long cable runs are necessary.
Recently, while doing some A/B comparisons, with a friend, between a PrimaLuna, Dialogue, Premium HP, tubed power amp and a VAC, Phi-200, tubed power amp, I had a mind changing experience. We intensely listened and compared both amps through a pr. of Wilson Audio, Sophia-II speakers. We listened to the PrimaLuna, using the EL-34 tubes and the KT-88 and KT120 tubes. While the EL-34s sounded smooth and warm, the PrimaLuma needed the KT-88s or KT120s to come close to the overall, dynamics, power and presentation of the VAC. While the PrimaLuna, sounded very nice, indeed, it was not quite on par, in terms of dynamics, detail and overall scope of the stage, with the much more expensive VAC. Then we decided to run the VAC through it’s XLR, balanced circuit. I thought nothing could be better than what we had already heard, but WOW! Switching the VAC to XLR was mind blowing. We switched back and forth several times, ea. time concurring what we heard.
As mentioned by others - running XLRs, if your amp’s XLR posts simply tie into the RCA circuit and the amp doesn’t have a dedicated, fully balanced circuit - will net no gain. I’m now convinced, however, that with a very good amp, having a true, fully balanced circuit - I would choose the XLRs...IMO...Jim
