Hello!
This comes up from time to time. The RCA and XLR outputs of the TX102 pre-amps are actually the same signal wires inside the pre-amp. If you hook up both RCA and XLR's at the same time you'll ground pin3 of the XLR via the RCA' outputs ground connection - less than ideal for the ballanced connection!
From time to time there are folks who would like to play with XLR outs but also feed a subwoofer from an RCA output. I have had times when I wanted to do this myself. To address this Jonathan from S&B has suggested feeding the RCA output from (you guessed it!) a transformer. This breaks the ground connection to the RCA output and so both can be hooked up together.
The transformer we'll use for this application is not terribly expensive. It's a model 761 from S&B. It has good low fequency response and will cost about $40.00 or so per channel to add it. Info on that transformer is here:
http://www.stevens-billington.co.uk/page761.htmThanks!
John Chapman
www.bentaudio.com