These sound really nice with lower powered tubes such as the 12AT7 or 12AU7, et. Adds a nice quality to my Ampeg Micro VR stack, but I even use it for killer crunch into my Portaflex T50. Lots of musical greats used these pedals, nuf said. Get it if you can find one. I just bought the plain Blue Tube version to add some variety in tone. I'll put an AT tube in one and an AU in the other.