Threshold Sa3.9e

Hello, is it possible to have the manual of this fantastic amp?
I am particularly worried about the possibility of driving the 3.9e from my Aleph P1.7 preamp in balanced mode, because I have read that the xlr input impedance of the power amp is only 600 ohm while in the P1.7 manual it is recommended to keep the master volume in the position of least attenuation (where it has the highest output impedance!).
I can't find anything on the web........
Thanks,
Stefano