Maxon has re-released the fabled AF-9 auto-filter. Whether or not this thing is truly a Mutron *clone* like all the hype states I dunno....but it is Opto-coupler powered! Not sure about that hefty price tag...You can by a vintage one for about the same I think?? "The AF9 Auto Filter takes the most desirable auto-wah and swept filter effects and offers them up in a compact, user-friendly package. Opto-coupler circuitry produces the shimmering, watery filtering of legendary vintage units. Threshold and Peak sliders control the degree of effect; while Range and Drive switches determine range and direction of the filter sweep. Three selectable filter types (Low Pass, Band Pass, and Hi Pass) and a frequency range of 100 Hz - 4 kHz allow the AF9 to function with virtually any instrument or input signal."