turntable B's music. The other points along the crossfader's path produce different mixes of A and B. DJ mixers typically have phono preamplifiers to hook up turntables. The signal that comes directly out of a vinyl turntable is too weak to be amplified through a PA system. Before a turntable can be usable in a mix, it needs to be preamplified. DJ mixers are also used to create DJ mixes, which are recorded and sold. DJ mixers usually have equalization controls for bass and treble of each channel. Some 2010-era DJ mixers have onboard electronic or digital effects units such as echo or reverb. Some DJ mixers also feature a built-in USB sound card to connect to a computer running DJ software without requiring a separate sound card. DJ mixers typically have a microphone input, so that a microphone can be plugged into the mixer, enabling the DJ to announce songs or act as a master of ceremonies (MC) for an event. Some DJ mixers have a kill switch, which completely cuts out a channel, or, on some models, completely cut out a frequency band (e.g., all the bass). Outputs The output from a DJ mixer is typically plugged into a sound reinforcement system or a PA system at a dance, rave, nightclub or similar venue or event. The sound reinforcement system consists of power amplifiers which amplify the signal to the level that can drive speaker enclosures, which since the 1980s typically include both full-range speakers and subwoofers for the deep bass sounds. If the DJ is performing a mix for a radio station or television station, the output from the DJ mixer is plugged into the main audio console being used for the broadcast. If the DJ is performing a mix that is being recorded by a recording studio, the output from the DJ mixer is plugged into the main audio console used for the recording, which is in turn plugged into the recording medium (audiotape, hard disk, etc.). In some cases, such as when a DJ is performing a set at a club for dancers that is also being simultaneously broadcast over the radio or television system or recorded for a music video or other show, the output from the DJ mixer is plugged into the sound reinforcement system and into the main audio console being used for the broadcast and/or recording. At club sets, some DJs