AB_LM is a gain control which enables level matched and sample accurate AB comparison of FX chains. Plugin (FX) or even a complex FX chain to the sound. Most DAWs can easily enable/disable (AB) single plugins or even whole FX chains, but in most case there is an audible loudness difference between both cases. In order to compare the impact of a plugin chain objectively the loudness of the incoming signal should match with the loudness of outgoing signal. Comparing the plugin effect at equal loudness levels avoids the “louder is better” – pitfall.
Mode & Link Channel
Sets the mode of the plugin, either Sender or Receiver and the link channel for the communication. Sender is placed before the plugin(s) which should be AB level matched, Receiver is inserted after.
Some plugins add latency to the plugin chain. For a sample-exact AB loudness comparison audio streams need to be synchronized. This can be done automatically (just press PDC button and wait 1-2 seconds) or manually by entering the latency value (in samples).
This meter shows the current and maximum loudness of the audio stream just before the plugin(s). Many plugins work best at a certain loudness level (e.g. -18 dBFS)
This meter shows the loudness difference of pre and post-FX signal. The match button lets you set the additional post-FX gain (match mode “manual”) based on current loudness difference. Match mode “Auto” does this automatically.
AB-LM lets you match the loudness either manually, or automatically.
The mode “Gain Stage” works differently: The additional FX drive gain is just removed from the audio stream right after the FX chain for “pure” gain staging purposes.