In the end Cardas made me a couple of adapters with the 3-pin floated, with no extra charge for the custom order. I've had a few days to A/B the RCA vs. XLR outputs and to play with the attenuation jumpers inside.
Results: XLR output > adapter > unbalanced interconnect > amp is clearly better than the RCA out, which revealed an audible graininess on congested peaks and some sibilants. The XLR was much, much smoother.
I also preferred the -10dB jumper setting, which was quite close in output level to the fixed-level RCA outs. The -20dB setting was a little anemic, while in my setup the dynamics from the the 0dB output were a little flat. (Benchmark recommends using a jumper setting that yields normal listening levels north of 11:00 on the DAC1 volume control, and to do so I had to turn the stepped attenuator on the tube integrated from noon to less than 10:00.) -10dB was the Goldilocks setting for me.
Going forward in my setup, the XLR outs with adapters will feed my amp and monitors, while the RCA outs will go to the stereo subs.
Bottom line: if you're using the RCA outs, getting the $58 Cardas adapter (Moon Audio sells 'em cheaper than Music Direct) for the XLR out is a clear improvement.
Results: XLR output > adapter > unbalanced interconnect > amp is clearly better than the RCA out, which revealed an audible graininess on congested peaks and some sibilants. The XLR was much, much smoother.
I also preferred the -10dB jumper setting, which was quite close in output level to the fixed-level RCA outs. The -20dB setting was a little anemic, while in my setup the dynamics from the the 0dB output were a little flat. (Benchmark recommends using a jumper setting that yields normal listening levels north of 11:00 on the DAC1 volume control, and to do so I had to turn the stepped attenuator on the tube integrated from noon to less than 10:00.) -10dB was the Goldilocks setting for me.
Going forward in my setup, the XLR outs with adapters will feed my amp and monitors, while the RCA outs will go to the stereo subs.
Bottom line: if you're using the RCA outs, getting the $58 Cardas adapter (Moon Audio sells 'em cheaper than Music Direct) for the XLR out is a clear improvement.