Balanced Line Tube Circuit

[Drone]

I've got this old (80's not vintage) tube head I used for recording various things through. I run some kind of preamp, or line signal into the AUX jack on it, the preamp on it being some horrible, thin, fizzy sounding thing with op-amp distortions built-in etc.

So basically I have two 12AX7's sitting in it doing nothing, as the AUX feeds more or less direct into the phase splitter.

I was thinking it would be nice if I could convert it into a balanced line amp, because I occasionally run signal from my 'control room' to the 'studio' (in quotes because it's really all one space) and it picks up a fair bit of hum on the way.