The Valvetronix + Series amps--which include the more powerful VT40+ and VT80+-also feature a Power Level control that allows you to reduce wattage in the output stage to control volume while preserving tone and dynamic response. Pressing and holding the Preset button for a couple of seconds activates Manual mode, where you can create your own amp and effects combinations, tweak them to taste, and save them to any of the eight user memory slots via the bank/channel buttons adjacent to the input jack.
Thompson, Art (2014) Vox Valvetronix VT20+. In: Guitar Player, Vol. 48, No. 10, pp. 116. Available at https://openmusiclibrary.org/article/765326/.