Separate bass amplifiers which do not contain speakers, often called "heads" or "amp heads", are usually integrated units, with a preamplifier, equalizer (bass and treble controls) and a power amplifier combined in a single unit. Some bassists use separate preamplifier/power amplifier setups, where one or more preamplifiers drive one or more power amplifiers. In the latter example, a bass player can use a bass-specific power amplifier or use a sound reinforcement system power amp. Bass amp heads are available in high-wattage power ratings that are not available in combo units. For example, the Ampeg SVT8-PRO amp head puts out 2,500 watts RMS at 2 ohms, a power level that is high enough for the largest 8x10" cabinets and the largest venues (stadiums, outdoor festivals, etc.).