You need the famous Morley PBA-2 Dual Bass Wah for that funkin', slappin', groovin' kind of sound. But sometimes a more straight-ahead vintage effect is called for. Just step on the button and you're playing a Traditional Wah. The PBA-2 is 2 super high-end pedals for the price of one. Features a wah level control. T.M. Stevens, Bill Dickens, Rudy Sarzo, and Dave Pomeroy tread on it all the time. If it's good enough for them, it's good enough for you. The Dual Bass Wah Pedal is also good for 7-string and detuned guitars.
Missing Rubber Foot Pad