I bought a Peavey Valveking 50 watt 112 combo about a year ago. I have been busting its balls trying to get it to fail. These are the issues I noticed and my solutions.
Fizz: As the amp gets louder all the tone settings need to be tweaked. Many pros use an EQ both before and after the preamp. After the amp has warmed up for ten or fifteen minutes it sounds 100% better.
Reverb: The screws in the reverb pan are correctly installed. A reverb should be able to "float" a little to avoid resonance feedback. The two (instead of four) screws in the reverb pan aren't supposed to be tight. I like the sound of the stock reverb.
Intermittent Crackling: When using an outboard distortion pedal balance the gain of the pedal with the amp gain. As the amp gets louder less distortion from the pedal is needed. This may not be acceptable for high-gain metal.
Speaker: The stock VK speaker is fine for semi-pro blues or classic rock players. If full volume and balls-to-the-wall distortion are needed a speaker upgrade may be necessary. Please keep in mind it is only a 112 open-backed combo, not a stack.
Tubes: No issues
Bedroom Jamming: Preamp distortion is ok for me at lower volumes. If you want power-tube distortion at bedroom levels get a smaller (5 watt or so) tube amp or an attenuator.
Channel-switching Delay: If it is a problem contact Peavey. There is a simple fix.
Durability: I have tried everything to kill this amp (short of sledgehammers and water immersion.) It just won't die or malfunction.
My conclusions are:
This amp must be tweaked. It is not plug and play. Peavey amps tend to be this way, some more than others. The Peavey Valveking 112 50 watt combo is perfect for intermediate and semi-pro users. The stock speaker sounds much better with proper break-in. For high-gain metal and punishing volume a speaker upgrade may be advisable. My particular VK is rock solid and sounds great. Plenty of headroom, sparkling cleans, good punch and all flavors of distortion. Great sound, great price. In twenty years it will be a closet classic.
I second that, since my experience with my VK112 is pretty much exactly the same. The thing is, quality control isn't so good, so some people have been getting lemons while some of us get the good ones. This creates a lot of mixed reviews, especially word-of-mouth stuff here on UG.
Telecaster - SG - Jaguar
Princeton Reverb, Extra Reverb
P-Bass - Mustang Bass
Apogee Duet 2 - Ableton Suite