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AB_LM (AB Loudness Match)

Product description

AB_LM is a gain control which enables level matched and sample accurate AB comparison of FX chains.

We at TBProAudio found us very often in mixing or mastering situations where we need to quickly identify the contribution of a certain plugin (FX) or even a complex FX chain to the sound.

Most DAWs can easily enable/disable (AB) single plug-in 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. Use the "L"-button (auto) to quickly set next highest (free) sender/receiver channel. In addition AB_LM makes suggestions for channel auto link, which may work depending on DAW/plug-in type.

Latency Compensation

Some plug-in 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).

Pre-FX Loudness

This meter shows the current and maximum loudness of the audio stream just before the plugin(s). Many plug-in work best at a certain loudness level (e.g. -18 dBFS)

Post-FX Gain

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.

Match Modes

AB-LM lets you match the loudness either manually, or automatically. The match gain is added after FX chain. If "inverse" is enabled match gain is added before FX chain. 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. 

Snapshot Slots

AB_LM provides 4 snapshot slots to store and recall settings for FX drive and Post-FX gain. So you can test your plugin chain with different gain levels, all loudness matched.

FX Drive

This parameter adjusts the additional pre-FX gain.

AB Switch

This button lets you seamless switch between pre and pre-FX audio signal.

Pre-FX Gain

This meter shows how close the loudness of the incoming signal is matched with a certain reference level. Many engineers work with loudness calibrated audio systems.


Demo version versus Registered version

In demo mode (without registering) the plugin mutes audio every 90 seconds for a short period. This could be circumvented by clicking on the "TBProAudio" logo within 90 seconds.


Please download AB_LM here.


Please order AB_LM activation key here.







Top Mix Tip: Using Reference Tracks - Warren Huart: Produce Like A Pro

DAW gain-staging

Customer Reviews

Obe1 (

... Looked into loudness matching plugins today and looked into this one because it was a better value than some of the others out there. WOW. A lot of the wow comes from the concept of loudness matching, but the plugin did all the work, and was pretty easy to use ...


- NEW: auto-connect during instantiation
- FIX: VST3 broken gain match function, match buttons no longer automatable

- UPDATE: make reset and match buttons automatable
- UPDATE: updated tooltip texts that match the manual

- UPDATE: small changes in registration process

- UPDATE: removed auto-connecting during start up (lost link fix). please refer to manual for autolinking

- FIX: VST3 Cubase read correct bypass state

- FIX: VST3 crash Adobe Audition 2020
- FIX: improved Ableton/Studio One compatibility

- FIX: AU validation

- UPDATE: improved channel menu

- FIX: global command handling

- FIX: global reset/match

- UPDATE: global reset of pre-gain diff and gain diff (shift mouse click)
- UPDATE: Pre FX, match max value, changed from shift mouse click to ctrl mouse click
- UPDATE: global match (shift mouse click)

- UPDATE: stepped level/gain mouse input

- Small GUI changes
- Info menu

- Ableton Live: Set "Disable Storage GainDiff" to default on
- GUI: fix wrong label for latency parameter

- Optimized background for HiDPI

- Disable auto update gain diff storage

- Fix for wrong gain differences if latency compensation enabled and DAW starts playing

- Measurement Methods: max peak level added (please review your settings if upgrading old projects)
- Delta Monitoring: works now with all match modes and AB switch (see manual for more details)
- GainStaging: show negative Post-FX gain values for positive Pre-FX/Drive values
- GUI: small fixes
- AAX: fix rounding int values

- Fix: Min/Max pre-gain/gain limits extended to -/+144 dB
- Fix: Meter display Post FX gain changed to exact opposite of Post FX diff

- NEW: delta monitoring (sender receiver difference signal)
- NEW: global activate/deactivate, match mode, ABFX, drive and delta monitoring (shift mouse click)
- PostGain: stored automatically

- AAX: button hang fix

- Code optimizations

- GainStaging: remove PreGain during AB off

- DSP code optimizations

- Gain staging fix: add. PreFXGain compensated
- VU Metering

- Fixed PDC bug

- Small bug fixes for issues which could cause incorrect measurement after a while

- RMS modes changed: RMS->RMS sum, RMS+3->RMS avg

- New GUI
- Fixed Pre FX max readout
- EBU filter denormal fix

- Auto link channel:
- works optimal in pairs
new plug in instance: even instance_count => sender, odd instance_count => receiver, next free channel is chosen (does not work for AAX/RTAS)
copy track with linked pairs: sender/receiver pair is re-linked (does not work for AU and AAX/RTAS)
copy plug in: next free channel is chosen

(Attention: Please remove all instances of AB_LM before installing V1.3.0 (incompatible parameter set))
- Added auto channel select
- Link channels extended to 256
- RMS/EBU measurement bug fixed

(Attention: Please remove all instances of AB_LM before installing V1.2.0 (incompatible parameter set))
- Adds Measurement Modes EBUR128 ML (400ms) and EBUR128 SL (3000ms)

- Small GUI fixes

- Inverse gain match switch
- Link channels extended to 32

- Fixed crackle in auto gain mode during startup

- Demo "Stutter" fix

- Initial release