Add direct monitoring between preamp and AD

 
Hello to all,
I want to use this rack I have around to place my green preamps and put it together with a high qualityAD.
This interface is from a dead company, but even the audio section was a little noisy (supplied from the PCI card from computer), it had decent audio section.
  What I want to do is use the front panel use the monitoring section it has.(if posible)
I have the schematics that are public on the web since the company dead, (atached the monitoring section)
My doubts are how to split the signal on this circuit to no loose quality on the signal sent to the AD.
In the other hand the preamp out to the Ad is balanced, while this monitoring section is not balanced.
  I should like to know your opinions if could insert the signal on any point on this schem for monitoring, and if have to remove some things like some pot or so, to avoid interaction between preamp out, AD in, and this circuit.
  -The circuit is for monitoring two preamps and two line inputs, but I should use this line inputs for monitoring two aditional preamps.
  -The signals the arrive to the first four level pots are coming from preamps (the first two), and from line inputs amplifiers),
  -DPDT swtiches, S1,S3,S5,S6 original was to send the signal to the AD, I don´t think this a good idea, since I should like to not add any aditional circuity between the preamp and the AD (if i´s posible).
  I attached the pdf, hope anyone can give me opinions.
Thanks in advance.

  Have searched the forum, found some thread about splitting preamp signal just with one Y cable.
This thread is what I´m after: http://www.groupdiy.com/index.php?topic=23525.msg279459#msg279459

From the point of view of the singer, it´s nicer to have a direct analog monitor, than coming from AD/DA,
  I´m sure many guys here can give me a light just looking a moment the schem,  maybe it doesn´t worth to use that?  Just build my own micro-mixer to mix the preamp-output with the computer output?
  My doubts are how can split the balanced preamp output (supergreen version of the green), and mix it with the DA out, that is unbalanced. Too complicated?  Too simply stupid question here?