The MXR classic overdrive pedal has a hidden switch inside that changes to the Zakk Wylde overdrive. I've seen people mod their own switch for it, but I just drilled a hole
MXR Classic Overdrive Pedal | Reverb
MXR Dunlop M-66 Classic Overdrive White Guitar Effect Pedal + Original Box | eBay
MXR Classic Overdrive Pedal | Reverb
MXR M193 GT-OD Overdrive Pedal | Sweetwater
The MXR classic overdrive pedal has a hidden switch inside that changes to the Zakk Wylde overdrive. I've seen people mod their own switch for it, but I just drilled a hole
MXR® GT-OD - Dunlop
MXR Classic Overdrive Pedal | Reverb
MXR Classic Overdrive Pedal | Reverb
Versus: MXR Classic Overdrive x Maxon OD 808 Overdrive - YouTube