A digital vinyl system normally uses special
vinyl records which are played on conventional
turntables. The vinyl is a recording of analog audio signals often referred to as
timecode. The turntables' audio output - the timecode recording - is routed into an
analog-to-digital converter, or ADC. This ADC may be a
multi-channel soundcard or a dedicated external
USB or
FireWire audio interface box,
DJ controller device or compatible
mixer (usually distributed with the software). The ADC sends digital time code information to the software, which then translates the signal into corresponding changes in the playback speed, direction, and position of a digital audio file. The audio file will react as if were pressed directly onto the record. The manipulated audio output of the program is then sent back through the
DAC or the computer's sound card, and can be routed into an audio mixer where it can be mixed like any other analog audio signal. The result is digital audio playback that sounds like music manipulated by an analog vinyl recording. However, there is always a short delay between the needle's reading of the time code and the software's playback of the audio. The delay time is treated as a
figure of merit for vinyl emulation products. A shorter delay allows the DJ to have better response and control of the music and is usually not noticeable by the user or listener. In some countries, for example
Finland, a
digital DJ license is required to legally play copyrighted music publicly with vinyl emulation software. == Software packages ==