It's relatively easy once the board is computer designed and proven, it can be made out commercially then at a reasonable cost.
I've done it.
To make one at home, with an etching pen etc is very tricky when using 16 pin ICs etc and therefore tiny tracks.
I've also been there, done that , it's a black art.
I'm contemplating making a much, much simpler echo than Jean Claude's and may well make a proper PCB after doing a prototype.
A thousand thanks to him for the spark, the fundamental notion of using one echo chip per recording head. Magnifique !
I still have a certain amount of equipment having done this sort of design and construction in my time as an electronic engineer , heated bubble etchant tank, wash tank ,ultra violet photo developer etc, but to contemplate making even a few PCBs in this way is a no-no for me.
Here's a PCB I designed, this was sourced out after doing the prototype.
You can just make out my name and old phone number on the right hand side.