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XLR to RCA output conversion on Benchmark DAC1

I've all but decided to pull the trigger on a Benchmark DAC1 HDR. It's got two sets of outputs, balanced XLR and unbalanced RCA. I will need to use the Benchmark as a preamp, controlling volume sent to 1) an integrated tube amp and 2) a pair of powered subs in stereo.

Both the amp and the subs have only RCA inputs, so I'll need to convert the XLR output on the DAC1 to unbalanced. In the owner's manual, Benchmark says "If the balanced XLR outputs are wired to an unbalanced input (using a special adapter cable), pin 3 must be left floating. Shorting pin 3 to ground will increase the temperature of the output drivers, will increase power consumption, and may cause distortion."

All the adapter manufacturers I have found to date (including Cardas) indicate that the 3 pin is tied to ground, but Blue Jeans Cable will make an interconnect with custom terminations that should fit the bill.

Question is: should better results come from using the converted XLR output to send signal to the amp, or to the subs? Once converted, of course, the XLR output will travel unbalanced. I know that XLR output voltage levels are higher than unbalanced ones, but the Benchmark has an internal jumper to attenuate the level of the XLR out. I can further use the volume control on the subs and the volume on the integrated to fine-tune the relative levels. The interconnect run from the DAC to the subs is 5-6 feet; to the amp is 1.5 feet.

Thanks in advance for your thoughts.
cymbop

Showing 2 responses by cymbop

cymbop OP
315 posts
 
Excellent news, Duke, that you had good results with the adapter interconnect.

Follow-up question: Would I be better off sending the XLR > RCA output to the integrated, or to the subs (which are low-passed at 45 Hz)? The integrated will be doing 95% of the musical work, so it ought to get the best signal. If I'm using adapter cables, I'll have to decide beforehand to order the right length.
cymbop OP
315 posts
 
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.
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