SAE model a105 subwoofer power amplifier input options

This SAE model a105 subwoofer power amplifier is two channel and has speaker line inputs for the left and right channels. It outputs to left and right subwoofers.

I am of little brain but believe that the current from the amplifier speaker out is different than the pre-amp to amplifier out.

Is there a line buffer or some fix to use the pre-amp subwoofer out's from my HT pre-amp as input to the a105 speaker inputs?

If anyone has any leads or links to the manual that would be very helpful. I can't seem to find it.

Much obliged.