Check out the Iron Age Audio Portia Street Stomp, it's a passive transformer in a box, with primary and secondary loading pots to get different colors from the driving and receiving amplifiers. I wonder what potentiometer values they used. There's a demo video on YouTube by Seawell Studios if anyone wants to hear it.
There's also the Avedis TransDriver which seems somewhat similar. Maybe not as much color as some of the other things mentioned in this discussion.
There's also the Avedis TransDriver which seems somewhat similar. Maybe not as much color as some of the other things mentioned in this discussion.