Cons of using main XLR/Balanced outs for subwoofer?

Dear @zdw11 :  as @imhififan  posted go a head no problem at all and you don't need to make any added mods.

Btw, did you try it? if not then do it and you will be the best judge about. Don't worry you can't damage nothing with that set up.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

@cardani  If the RCA outputs are in parallel with the balanced outputs on your preamp then what you describe makes sense. If it were me I'd be using the Jensen ISO MAX subwoofer transformers to do the conversion and not use the RCA outputs of the preamp at all.

Dear @cardani : " Two of these op-amps are to buffer the signal to the tape output and level control, the remaining four for the two balanced outputs. These integrated circuits are specified as delivering high output with low noise. "

that comes from the design in your Bryston. So the problem could comes from that Dayton unit.

Now you said: " higher noise floor ". Could you detected around wich frequency of that " noise floor " ?

In my system I run my two subs from the balanced preamp outputs and the main amplifiers running with the unbalanced outputs and both performs with no single trouble/noise or the like but with very high quality level performance.

Even that your Bryston is not a today model it’s and has very good design as everything Bryston puts in the market, seems to me that noise floor level is not developed by a " failure " in the unit design because outputs are buffered.

If that noise floor is really high then that ISO MAX can helps. In the other side you can always contact directly to Bryston asking for advise in that issue.
:  https://bryston.com/#contact-form

R.

@atmasphere Ralph, please explain the hookup with the ISO-MAX. I’m running the balanced main output from my preamp into the power amp. I’m running simultaneously the single ended main output into my sub. So, if I used the ISO-MAX for the sub, how would that be hooked up if you don’t recommend using the single ended output at all? Thanks.

You would run dual balanced outputs, one set to your main power amp. The other set would go to the ISO MAX units (left and right channels). Only at that point would you use RCA connections, between the ISO MAX units and your sub. So the ISO MAX units would be right by your sub so you could run a longer balanced line connection from the preamp to the ISO MAX. If you don't have dual outputs on the preamp, you would use some form of a Y adapter to make it happen.