Amp designer producing overly distorted and popping sounds
New to logic pro for a month now. Everything I have been doing is very basic. I am recording guitars through Apogee Duet 2 using amp designer and after initial hurdles for beginners got everything up and running brilliantly. Then out of nowhere, every head I select produces an overly distorted and popping sound when gains are more than 50%. It is especially noticeable when using the British heads. At first they all sounded amazing, very comparable to my JCM heads then this happened and I can't figure out why. I've verified its not my headphones or monitors, possibly its a configuration issue? Maybe messed something up unknowingly. I know this question is somewhat vague. Thanks in advance to anybody willing to assist.
Logic Pro X, OS X Yosemite (10.10.4)