Factory added Top Boost channel. 47k Ohm Bias Resistor runs hotter but breaks up at lower volume than the later 82k Resistor. Has both Tremolo and Vibrato features with selector switch and 3 preset speed settings for either effect. Best sounding AC30 I've had but the others sound pretty damn good, too! The 2007 AC30H2 and the 2005 AC30CCX (X for Blue Alnico speakers) both dance around the vintage Vox tones of the '61 in convincing ways and both are very useful both for live and studio applications. The 2007 Cream covered 50th Anniversary combo is for sale on eBay and Craigslist Los Angeles right now since I bought the '61 and have the 2005 I feel pretty well covered for Vox sounds! Hate to lose the beautiful blonde hand-wired anniversary RI but need the bucks at this time.