The MXR Classic Overdrive is keeping secrets; specifically, it houses a secret switch that turns this affordable overdrive into a Zakk Wylde ZW44 drive. This is essentially two pedals in one, and though it might not be very convenient to take the pedal apart to get the second circuit, it's hard to complain at this price point. The original circuitry has a more vintage flavor, while the Zakk Wylde circuit has a high-gain, modern sound.