RCA to XLR Adapter

I have a Herron pre amp that has only RCA outputs.  I'm considering buying a pair of used Merrill Audio Veritas Monoblocks that only have XLR inputs. I found these Cardas female RCA to male XLR adapters that would allow me to make the connection.  Are there any downsides to using adapters such as these? 
You just need to find out the wiring of the pins on your amplifiers input and have a cable made or modified. My preamplifier (Doshi, not full balanced circuit anyway) has XLR out and I called the distributor for the information. My amplifiers are RCA.
The section of the Moon Audio writeup cautioning against using adapters is talking about a completely different situation. There is no risk of damage in using RCA-to-three pin XLR adapters at the input of a power amp, and connecting RCA cables between the preamps’s outputs and the adapters. Of course, sonics most likely won’t be as good as if you were providing the amps with a balanced pair of signals for each channel.

There are a few preamp designs, especially some of those having transformer-coupled outputs and some others in which the outputs are "floating" relative to circuit ground, in which a hum might result from doing that. But that would be unusual and is not applicable to this case.

The need for caution usually arises when adapting XLR outputs to RCA inputs, not the reverse.

Also, you mentioned Cardas adapters. Like most other such adapters, most of those short pin 3 to pin 1, but some of them don’t. In this case I’m pretty sure it would be best to use the kind which shorts pin 3 to pin 1, which is what Cardas supplies as standard.

Finally, there are a few unusual designs, such as many or all of the Audio Research Ref series amps which only provide balanced inputs, for which using an adapter (and therefore not providing the amp with a balanced pair of signals) will result in a drastic reduction of the amp’s power capability, and an increase in distortion. I suspect that is NOT the case with the amps you are considering, as the ARC amps are unusual in that respect, but it would be prudent to check with the manufacturer on that point. If that turns out to be a problem, a pair of suitably chosen Jensen transformers (together costing ca. $300) connected between the preamp and the amps would provide the amps with a true balanced pair of signals for each channel, and resolve that problem.  And the Jensen transformer approach is very likely to be better in terms of sonics than an adapter approach in any event.

-- Al

If you make your own, be patient, twice check your connections, and try one channel at a time. 
If you get hum, obviously something is incorrect, check again😊
Been there, ”doing that,” satisfied w/the results. One day I’ll upgrade the cabling. Right now too many other, bigger fish to fry.