Cons of using main XLR/Balanced outs for subwoofer?

@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. 

Dear @zdw11 @cardani  :  I can see that both of you are running your main speakers/subs to listen MUSIC ( at least do not posted for HT. ).

Now in the Ohm speakers the sub is part of the speaker ( I don't know forsure all the subs controls to operation. ).

If we want to listen in specific MUSIC through our room/system and want to add subwoofers the rigth way to do it is that those pair of true self powered subwoofers crossover ( should be. ) around 80hz-90hz but this crossover frequency is not only for the low-pass subs but we need and should be that the main speakers been too crossing around that frequency with the high-pass filter and in this waythat room/system will takes a true advantages to add subs to listen MUSIC because in that way the main speakers will be handling frequencies from 80-90hz and up and the IMD and THD distortion levels that existed in those passive speakers goes really lower in benefit of higher sound reproduction quality level and at the same time that room/system will handled with accuracy the low bass range and even can goes lower in that range.

Due that I don't know of the overall Ohm speaker operation then I could be wrong with but with the other gentleman that's the rigth way to integrates subwoofers to MUSIC soun reproduction as our main system use.

Here a link about:

https://forum.audiogon.com/discussions/do-you-think-you-need-a-subwoofer/post?postid=310058#310058


Of course that one thing is what " should be " and the other what we like/want so in this specific subject everything is up to you and this post is only an opinion and nothing more.

R.