I've never had a problem running rca on one end and xlr on the other. You should be fine, the fewer connections the better.
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If you use an XLR to RCA adapter, you should check with the XLR-device's documentation or manufacturer to find out if shorting pins or floating pins is the correct configuration.
Also, you will be getting the equivalent to using a fully unbalanced RCA cable anyway, unless for some reason the XLR outputs on your DAC have different specifications than the RCA outputs.
Sometimes your source XLR circuit may expect a load on that negative polarity XLR pin. If you use an adapter, these output circuits may run hotter than normal (depends on how the circuit is engineer on the source/DAC). "Shorting that pin to ground" may not necessary work on these designs since there is no "load". The best way to do this is use a Jensen XLR-to-RCA transformer.