Everything I've read says the real difference between RAT units is in the parts tolerances of pot and caps (like most audio electronics, I guess).
I'm building because I like to build the stuff and then use it.
All the effects pedals I built last year are now part of the core tone I play thru, whether it's into an amp sim or a tube amp.
The Naga Viper.. I had actually never even heard of it until you started posting clips using it. That tone is killer, so I figured it would make a fun little project!
