How to go from RCA to XLR?


I've got an Aragon Stage One processor with RCA outputs and two Aragon Palladium 1K monoblocks with XLR inputs. I know there are a lot of RCA-XLR cables available, but a fabricator told me you have to know which XLR pins are "hot" and these have to match the amps' input circuitry or you will damage the amp.
So how do you know which pins to make hot when you order the cables? When you buy these cables "off the shelf" are you just hoping you get lucky and they match up with your equipment?
Thanks
noslop
Great answer, Al. Thank you very much.
Could I use the "ground prong" (the round "3rd" prong) on the power cord's plug to check for continuity with the ground pin on the XLR input?
Scott
I'd suspect so, but I'm not sure that would necessarily be true with all equipment. Try it and see. If you get continuity to one of the xlr pins, you've verified that that pin is ground. If you don't get continuity to any pins, then that approach won't provide you with an answer. Same goes for measuring to chassis.

By "continuity" I mean something very close to 0 ohms (or at most say 1 or 2 ohms), as measured on an ohmmeter, not just an indication from a buzzer or other rough continuity checker which could indicate continuity even if a significant resistance is present.

Also, when you measure it would be prudent to have all signal cables from other pieces of equipment disconnected from the amp, so that your measurement is not confused by any possible paths to ground through the other equipment.

Regards,
-- Al
The standard for US equipment is pin 2 hot. Europe and most japanese brands use pin 3 as hot. It really doesn't do anything but reverse phase if it is not same, as Al stated.
Got some really bad news from Aragon tech support. Changing the XLR to XLR cable to an RCA to XLR cable, will cause the amp to run at only half power. Said half the input signal is grounded out so the amp, so the amp only puts out half power. Great.
Sounds like you need a single ended to balanced transformer like the Jensen model.