Systems and methods for fast activation of slaves during wake up in an audio system allow a master device in an audio system such as a SOUNDWIRE audio system to send system and/or topology information to capable slave devices during a wake up window so that the slaves may start in an active mode rather than a safe mode. In the most recent proposed versions of SOUNDWIRE, there is a check PHY_Num phase. The systems for fast activation of slaves cause a negative differential line to be driven with an encoded signal by the master during a check PHY_Num phase where the encoded signal indicates a fast mode speed. Capable slaves may then begin in a fast mode rather than a safe (and slow) mode. Latency may be reduced by starting in a fast mode, which may improve the user's audio experience.