I have one of the last DC5 heads made so I'm assuming that any upgrades from previous versions were installed. That being said, my reverb is the weakest of all of my amps. I have to go to 7 or higher to get anything resembling a spring reverb. I've changed tanks, cords, and tubes, nothing. I should say that I am comparing it to my Lonestar Classic and various Fenders (BF Twin, Concert II and a Vibro King) and a Bogner Shiva. When ever I need reverb on it, I use ourboard effects.