So I just scored one of those from a pawn shop for what I think is a good price (225$USD) but of course, it couldn't be perfect. So, I had a couple questions for you guys that still own those. 1) When turned on the amp exhibits some noise/hum that goes away as the master volume and boost controls are turned down. Nothing crazy but I was wondering if it should be 100% silent. My MB200 wasn't, even with headphones, so, I assume this has to do with the Class-D thing. 2) When I push on the horn ON button, there is a constant high pitched humming that sounds like water pouring in a sink. It goes away if turned off. Most likely a blown tweeter. Not a deal breaker as I don't use them... but still. Repairable or would have to replace it? 3) When the amp is turned on and headphones are connected, there is a loud pop coming from the speakers. Also not a deal breaker to have to turn off the amp but I'd rather not have to. UPDATE: Actually picking up radio quite well on this headphone out. 4) Doesn't seem THAT loud for a 500w amp. "How" loud is yours? 5) Anything else I should check before my 1 month warranty expires? All in all very happy but kinda cautious. Sounds killer and weighs less than half my Mesa Powerhouse cab!