Mainline - Balanced and Unbalanced expected behavior

[e2o]

Hello!

Finished my Mainline about a week ago, and I'm loving it! I had been using only balanced on XLR until the other day when I tried outputting to both XLR and TRS jacks simultaneously. I wasn't really thinking (my solid state amp has two outputs and I do it all the time.) Well, it worked out of both. It works out of both whether the output switch is set to Bal or Unbal. When I'm listening with just XLR, flipping Bal to Unbal appears to have no effect. When listening on TRS, flipping from Unbal to Bal results in lower volume, but they both work.

Is this expected behavior?

Photos of the wiring on Imgur here: https://imgur.com/a/RQA3Fy9

Thanks!

\ eric

[Paul Birkeland]

That is totally normal.  I also believe that the sound out of the TRS isn't going to be so great with the switch set to balanced.

[e2o]

That is totally normal.  I also believe that the sound out of the TRS isn't going to be so great with the switch set to balanced.

Thank you, Paul! Is there a description somewhere of what exactly happens when going from Balanced to Unbalanced? I'm curious as to a few things:
1) Is anything happening to the XLR when flipping this switch?
2) Is Unbalanced only using one side, the other side sitting idle?
3) If I do want a listening session out of both (unlikely), would it be better in Bal or Unbal mode?
4) Curious - why have the Bal/Unbal toggle? Why not have Unbal to TRS and Bal to XLR?

thanks again!

\ eric

[Paul Birkeland]

The audio ground moves from one end of the output transformer secondary to the center tap of the output transformer.  There isn't a way to have the 4 pin jack be a balanced output and to have the 1/4" jack doing what it's supposed to be doing.  If you want to listen out of both jacks, I would set the amp to unbalanced output, which will give you the full TRS signal on the XLR jack and the proper output on the TRS jack.

The schematic in the manual shows how these switches are laid out and how they connect.