+4Bu to -10dBv and vice-versa

Hi All,

I'm new to this forum but I did do a search before I posted this and the most hopeful thread was from 2012 and most of the links were broken.

I'm looking to build a transformer based box which can interface a -10dBv reverb with my Audient ASP4816 console which runs at +4dBu.

I have seen some boxes that do this including:
CANFORD PRO-INTERFACE MK 2 - Free standing - Canford

I coud just buy one but in the spirit of DIY, I'd like to build it myself.

Any tips or advice on making such a box?