I’ve got a Luxman R-115 that I want to hook a sub to. It does not have a subout jack. It has a preout, but no main in. I know I could use the speaker outputs, but would rather like to feed a line level signal to it instead. Could I use the tape rec out jacks? It has in and out jacks for use of signal processor or similar device. Which would be better or what problems could there be? Thanks!