Like all Fulltone products, the 70's fuzz is incredible. Really works well with Marshalls. I can't speak for Fenders. I also own a vintage Orange amp and it works well with that too. But with my Marshall it is off the charts fuzz heaven. I have owned dozens of fuzz box. Numerous Big Muffs, Fuzz Face, Soul Bender, Tweak Fuzz, etc., etc. and until I got the 70's fuzz I was never totally happy with any of them. Every tone is vintage and classic. Adjusting the volume knob brings out so many classic fuzz tones that totally impress. Fulltone is by far my favorite pedal maker.