My current hunt for my "perfect" OD tone has lead me to give the EH English Muff'n a run - I have a fondness for the tone of overdriven tubes. In stock configuration, the 12AT7 tubes in the Muff'n offer a range of sonic options from clean tubey warmth to full-on fuzzed-out dirt. Despite much knob tweaking, I just wasn't finding the tone that made me go, "Yeah, baby!" As an experiment, I dug through the parts box and found a pair of fairly new Fender/Groove Tube 12AX7s, and installed them in the Muff'n. Ah-ha!! The "TONE"!!! With the gain dialed at about 50%, I'm getting a lovely smooth OD with lots of grind without being too over-the-top-fuzzy. The higher gain of the 12AX7s, but lower gain setting on the pedal, has turned out to be a great combination. In the future, I may experiment with a set of lower-gain 12AU7s and push them harder.