LA9B Levelling Compressor

The LA9B is a simple, great-sounding levelling compressor for vocals, instruments and full mixes. One main dial does the heavy lifting, so you can spend less time tweaking and more time listening. Optional Input and Output Xformer stages add the gentle, level-dependent saturation of analogue transformers.

Please note: the LA9B is an original design and is not related to, or a model of, the famous LA2A Opto Compressor.

FEATURES:

  • One-dial compression: just turn Compress until it sounds right.
  • Two modes (A and B) with different characters – try both.
  • Input gain, output gain and Auto Level matching.
  • Input Xformer and Output Xformer: switchable analogue transformer saturation, voiced differently at the input and the output. Saturation LEDs show how hard each transformer stage is working.
  • 4x oversampled, linear-phase transformer processing, with latency reported to your DAW.
  • Optional Side-Chain low-cut to keep bass from over-triggering.
  • Stereo Input and Output meters, plus a Gain Reduction meter.
  • Clean, simple layout – every control is on the front panel

TRANSFORMER STAGES:

The LA9B has two transformer stages: Input Xformer and Output Xformer. Each is switched ON or OFF with its own button, and each is OFF by default.

Where they sit in the signal path:

  • Input dial (-12 to +12 dB)
  • Input Xformer
  • Compressor (Side-Chain detector, Compress, Mode)
  • Output dial, or Auto Level when it is On
  • Output Xformer
  • Output meter

Because Input comes first, turning it up pushes the Input Xformer (and the compressor) harder. In the same way, the Output dial, or the level chosen by AutoLevel, sets how hard the Output Xformer is driven. The compressor and its Side-Chain detector hear the signal after the Input Xformer.

What each stage does:

Inside each stage, the audio is processed at 4 times the host sample rate (4x oversampling) to keep the saturation clean, in this order:

  • Low-frequency boost (low shelf) before the saturator, so lows are driven harder than highs
  • Soft saturator: a smooth, symmetrical curve with no hard threshold, producing mainly odd-order harmonics
  • Matching low-frequency cut after the saturator: the exact inverse of the boost
  • Low-end bump: a fixed, mild boost in the bass
  • Gentle high-frequency roll-off
  • DC blocker, to remove any offset created by the saturation

Because the cut exactly undoes the boost, the stage is spectrally flat for quiet signals. Saturation rises with level and as frequency falls, so bass and loud peaks thicken first, and there is no sudden onset.

LA9B Levelling Compressor is a FREE plugin. It doesn’t require a license or any registration. Simply download (links below), run the installer, re-scan your DAW for new plugins and use.

I would love to read your feedback, comments or any bugs or issues you may find.

If you would like to support my work on free VST plugins, please feel free to donate any amount using my PayPal link. Your support is truly appreciated.

DOWNLOADS:

Windows 10/11 Installer: 

LA9B_Compressor_Windows_Installer_100.zip

Windows 10/11 VST3 Files: 

LA9B_Compressor_Windows_100.zip

macOS Apple Universal Binary Installer:

LA9B_Compressor_macOS_Installer_100.zip

Linux Debian Installer: 

LA9B_Compressor_Linux_Installer_100.zip

License:

LA9B Levelling Compressor is free software provided without warranty. You may use this plugin for personal and commercial projects. Redistribution or sale is not permitted.

Version History:

1.0.0: Initial release