For a few days, I experimented with 18V in to the Riot and the Fulltone FD2 and OCD (v4.) The biggest difference was with the OCD, and it was still fairly subtle. The FD2 had a very, very subtle difference, on its own, but using it to boost anything, the difference seemed to disappear. With the Riot, I couldn't really perceive any noticeable difference. There could be some difference, but if there is, I didn't really pick up on it. I kept the OCD at 18V, the Riot at 9V, and I'm still waffling over whether or not to go back to 9V on the FD2.