Well, I guess it depends on what you are looking for. I have ABd the Musitronics Mu-Tron III and the Has Mu-Tron III+ and, though similar they are different beasts. When used with my Skylark, the original Mu-Tron is not noisy at all. The Has version just doesn't get the depth and color of the vocal character of the Musitronics.
I haven't tried one of the Q-Tron family from Electro-Harmonix, but I've heard they are pretty good sounding and get pretty close to the original. Also, fairly new in the envelope filter pedal group is the
Guyatone Ultron -
here's a write-up from guitar player. I'd love to hear if anyone's tried one of these. At $425 they're not a lot cheaper than a vintage Mutron, but they look like they have a lot going on.
Peace
Tom
(Message edited by tom_z on January 15, 2007)