SIP (Solo-In-Place) Soloing a channel causes all other channels to be muted.
AFL (After Fader Level) Soloing a channel moves that signal onto a separate stereo mix bus, normally known as the AFL bus.
Sigma does not have a dedicated AFL bus. However, selecting the AFL option in SOLO MODE will hijack Mix Bus B and use this as an AFL bus. Sigma will automatically switch the monitor source selection to Mix Bus B when soloing in this mode.
AFL is useful when you want to solo a channel just to check something whilst printing a mix back into the DAW. If you were to use SIP, you would disrupt the printing process as soloing in this mode mutes all other channels.
Please note that if you are operating Sigma in AFL Solo Mode, you will be unable to route channels to Mix Bus B in the web browser. Also, upon changing to AFL Solo Mode, any channels currently routed to Mix Bus B will be un- routed.
By default, Sigma is set to SIP (Solo-In-Place).