As you will understand, this unit is older than most of the people at Eventide, and there is nobody here who knows anything about them.
But, I spoke to the designer, who although in his dotage, still has a few cells left, and he tells me the input clipping level is about +18dBm with about 90dB dynamic range. While lower than our more modern rack units, this is still respectable. It can be used with a nominal +4dBm line level circuit, with slightly reduced headroom (not usually a problem for a unity gain unit like this).
So, it should be entirely useable. Since you don't say how you are driving it, it is hard to know what problems you are having. You should be able to connect it to a mixing desk send and return, probably using balanced line XLRs (depending on your 1745's configuration). Adjust the input level for occasional flashing of red LIMIT indicator.
Do be aware that this is a very old unit, not really designed for modern live use. You should use it at line level, not guitar level.
Note that the manual says "Without transformers, input should not exceed 40V p-p, or 12V p-p on either line." These are quite high levels, so it should be easy to keep within this range.
