Those Valve King II amps have bang for the buck. As a home or studio amp, I think they're cool. I just have a hard time believing they'd put up with gigging, if that was the intent for the buyer. They look nice, but the parts have to be consumer grade to come in at that price point. Construction isn't an issue if it is handled with care. Tube guitar amps are a low fidelity technology, so cheaper parts don't automatically make something crappy.
The boost function does use diodes and it's setup kind of strange. I'd compare it to a Silver Jubilee, but puts the diodes later in the path. They are placed where a cold clipping stage could be and it gets an even clip, instead of the asymmetrical clip of a cold biased 12ax7. I don't mind that as long as it sounds good and Peavey made it sound good to me. They are in series with the signal and working like an overdrive (ala TS and others), rather than most "Metal" distortion circuits.
The class A to class A/B control, DI, and power soak are great features. I watched a guy play one at a local Mom and Pop shop and I was impressed. When I get around to shopping for another amp, I'm going to test drive one for myself.
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2007 3 Channel Dual Recto w/loop mod
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