Recieved mine in the mail today and I guess the resaler was as anxious to try it as I was. He popped open the ceramic disc and tried out my pedal for a bit, I didn't mind the footpring but opening the box for the first time is Oh, so much fun!
I plugged it in right away, both dials vertical and in single mode I punched in and my bass goes from clean to a nice, smooth almost fuzz, rather subtle, but lovely. I crank the gain a bit and it gets a bit clankier but still a slightly timid fuzz. I love it! Flip the switch to double, and the two faced beast goes from timid little schoolgirl to all out, in-your-face fuzz! Much harsher than the American reissue in tone, but warmer than the Sovteks, a perfect medium! It's very in your face, but still much clearer than it's Big Muff brotheren, as the treble pushes through, but so does the bass! It's chunky and still manages to let through a nice bassy tone!
But of course, the usual gripes with Electro Harmonix pedals...they're a tad noisy with active electronics and they have 1/8" 9V adapters. Other than that, I can't say a word, and who can argue with something they call a muff!
Long story short: Five out of five jumpy guys, great name, great sound, great pedal. Let's just not turn this into the OD250 and have everyone running out and buying one 'cause I love 'em.
The unit sounded great with both passive and active basses, the single muff mode with a passive P-bass was meaty and slightly overdriven, and became much more powerful in double muff mode. The unit added even more sweet, sweet growl to my active Stingray when in single mode, and became a best in double mode.
I play mostly heavy metal and the Double Muff is perfect for a sweet, almost tubey overdrive. Only slightly noisy with active instruments, but nothing to worry about live.