SPL IRON

An amazing sound from an all-original analog design
When SPL released the IRON mastering compressor, it became an instant icon. Their goal was to create a compressor that provided a pleasant, melodic-sounding, transparent compression, inspired by the vintage compressors of the radio era. But, they wanted it to be versatile enough to adapt perfectly to the needs of modern mastering studios. The resulting 25 lb, 4RU tube compressor was an immediate hit in top mastering studios around the world.

Inspired by tube classics, packed full of 21st century innovations
The IRON set a new benchmark by taking the sonic virtues of legendary vintage tube compressors and adding on modern innovations, including a parallel dual tube circuit, rectifier mode switching, flexible attack and release settings, and a High Dynamic 120V operating voltage.

Like two tube compressors in one
Unlike traditional Vari-Mu designs, which use a single tube for compression, IRON employs a unique dual circuit topology. A specially designed Mu-Metal iron transformer splits the signal between two distinctly different tubes—a 12AX7/ECC83 and a 12AU7/ECC82—each with a slightly different compression curve and feel. These two separate tube compression circuits are run in parallel, and then recombined to taste for a uniquely flexible approach to tube compression.

Far more control than any vintage Vari-Mu compressor
The IRON includes sidechain filters, and Attack and Release parameters that have six different settings ranging from Slow to Fast. These times vary according to the Rectifier circuit selected. Each of the six different Rectifier settings make use of different diode combinations—Germanium, Silicon, LED, and mixed for even more tonal variation. This added control means that mastering is not the only domain where the IRON sets new standards. It can also be used to process subgroups or individual signals, like vocals, bass, guitar, strings and more.

True analog modeling with the power of TMT
The SPL Iron is a TMT plugin, based on the patented Tolerance Modeling Technology by Brainworx. TMT gives you the most realistic analog sound in the box by offering multiple plugin channels with realistic analog tolerances in the components of the circuit modeling. Additional digital-only features include a monomaker, stereo width control, MS processing and more, making the plugin even more powerful than the original.

• Variable Bias Tube Compressor
• Parallel Dual Tube Circuit combines two tube types
• Custom Mu-Metal Iron Transformers
• Feed-forward resistive Vactrol-Opto-Isolator
• Six different Rectifier settings available
• Sidechain that allows you to choose between Off, four sidechain-filter presets or an external sidechain signal
• In Link mode, the Threshold, Tube Bias, Attack, Release, and Rectifier parameters, as well as the Sidechain EQs, are controlled with the right side (channel 2) of the unit
• Master out features an additional, Passive Equalizer with two fixed sounds
• TMT — Brainworx patent-registered “Tolerance Modeling Technology” (US Patent No. 10,725,727)
• Brainworx plugin only features such as TMT (US Patent No. 10,725,727), M/S Processing, Mono-Maker and Stereo Width, Parallel Mix and Headroom
  
  

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  Gentry Studer

  I downloaded the plug in, I've had to shoot it out against the real thing on every project, just to see how it stacks up. You guys did an amazing job with the plug in. Everything from the color it… Read More

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  Michael Romanowski

  Grammy Award-winning engineer (Alicia Keys, G-Love, Lady Gaga)

  I use the hardware SPL Iron for my mastering everyday. What I love about it is the tonal and dynamic flexibility is has for every style of music. And it’s always smooth and musical. Brainworx… Read More

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  Brendan Duffey

  Grammy-winning Producer, Mix & Mastering Engineer (Kendrick Lamar, Bruce Dickinson)

  When I need a tool that gives me a plethora of gain, tone and shape controls the Iron Mastering Compressor is the first thing I turn to. The Iron Plugin has all the controls features of the… Read More

• Really wow

  ★★★★★

  by White Heat

  February 28, 2025
  I have not purchased a plugin for 3 years. I am building a mastering chain and wanted a vari mu type compressor. I don't know how to use it yet but the compressor has a sound that has me wanting to… Read More

• Analog 3D sound

  ★★★★★

  by MiamiDude

  March 11, 2024
  Great for that analog sound, with depth and 3D sound! Great comp!

• Fernando

  ★★★★★

  January 29, 2024
  Nice !

• SPL IRON

  ★★★★☆

  by DJ A-O.N.E.

  October 11, 2023
  Modern sounding vari-mu style compressor. Dances on the master bus and adds its own color and flavor. I was a little skeptical at first but, the once I started to dig into the sound of this beauty,… Read More

• better than his inspiration

  ★★★★★

  by Synthitize

  September 13, 2023
  Some give it inspiration from the Fairchild 670;
  But it is better because in addition to colorizing the sound like the 670, from a pure compression point of view, it is much better and it… Read More

Supported Plugin Formats
AAX DSP, AAX Native, AU, AAX AudioSuite, VST2, VST3

Supported Operating Systems
macOS 15 down to macOS 12
Windows 11 down to Windows 10

Mac
Intel, or Apple Silicon

PC
x64-compatible CPU

System Requirements
Display resolution: 1440 × 900px or 1280 × 960px or higher
Memory: 2 GB RAM