R7
2
I did some research on this awhile back, probably for the same reason ( I tend to plug other gear into the A4 for FX). The web seems to agree that using a balanced cable if you have a balanced out is the best option, even into an unbalanced input. I do it all the time and it works great.
I’d recommend Mogami 2534 cables if you don’t have any balanced TRS yet. Very high quality and can be had for a decent price (for high quality cables at least) off ebay.