Black Lion Audio B172A Hybrid FET/Optical Compressor

Full Description

Two legendary compressors in one

The B172A brings together two of the most respected compression circuits in recording history. On one side, you have a Seventeen-style FET limiter known for its fast attack and aggressive character. On the other, an optical compressor inspired by the classic 2A; delivers smooth and natural compression that enhances vocals, bass, and more.

This combination lets you harness the power of both compression types, either separately or in series. Use the FET to catch transients, then smooth out the signal with the optical circuit—or reverse the order for a different compression response. This flexibility makes the B172A an invaluable tool for mixing and tracking.

Flexible signal routing

The B172A’s AB-BA switch puts complete control over your compression chain at your fingertips. Switch between FET-first or opto-first routing directly from the front panel. Each configuration offers a unique sonic response, allowing you to tailor the compression to the needs of your mix.

If you need independent operation, simply set the switch to the third position to disengage the internal routing. This lets you use each compressor separately, making the B172A effectively two processors in one. Additionally, stereo linking lets you pair two B172A units for consistent compression across stereo sources.

Premium transformers for top-tier sound

Black Lion Audio has carefully selected high-quality transformers to ensure superior signal integrity. The optical side features a CineMag input transformer, known for its detailed and transparent sound. Meanwhile, both circuits use custom Chicago-wound output transformers, providing warmth and character while maintaining clarity. These premium components contribute to the B172A’s ability to handle everything from subtle levelling to heavy dynamic shaping without unwanted distortion.

Custom-designed T4B opto element

The optical side of the B172A features Black Lion Audio’s custom T4B opto element, the T4BLA. Designed to be the best T4B optocell available, it delivers consistent, musical compression with a natural release curve. The development of this component involved extensive fine-tuning to ensure optimal performance, making it a standout feature of the B172A.

This careful design approach means the optical compression behaves predictably and musically, ideal for vocals, bass, and other sources that benefit from smooth dynamic control. With the T4BLA, Black Lion Audio has refined an industry-standard design into something even more precise and reliable.

Built for professional use

The B172A is engineered for durability and high-end performance. Housed in a 2U rackmount chassis, it features a solid build designed for long-term studio use. High-grade capacitors in the signal path and power decoupling ensure clean operation, while a well-thought-out layout makes controls intuitive and easy to adjust.

With its powerful compression options, premium components, and flexible routing, the B172A is a must-have for engineers who demand versatility and quality in a single unit. Whether shaping transients, smoothing dynamics, or applying compression in a stereo mix, this hybrid compressor delivers the tools needed for professional results.

Features

• Dual compression design combining Seventeen (1176-style) FET limiter and 2A optical compressor
• Independent or series operation with switchable A/B and B/A signal routing
• Custom Black Lion Audio T4B opto element for enhanced optical compression
• CineMag input transformer for the 2A circuit ensures high-quality signal transfer
• Chicago-wound output transformers for both circuits deliver vintage warmth
• High-grade signal path and decoupling capacitors for superior audio fidelity
• Stereo linkable for paired operation with another unit
• AB-BA switch allows quick internal rerouting of compression order
• Dual-mono link option for flexible stereo processing
• Independent use of each compressor for versatile dynamic control
• Classic compression combination used in professional studios for decades
• Compact 2RU rackmount design for easy studio integration

Specifications

• Type: FET / Optical Compressor
• Number Of Channels: Stereo, Dual Mono Link
• Controls: Ratio, Attack, Release, Peak Reduction
• Ratio: 4:1 To 20:1
• Inputs: 2 X XLR, 2 X 1/4″
• Outputs: 2 X XLR, 2 X 1/4″
• Other I/O: 2 X 1/4″ (Link)
• Attack: Continuously Variable 20uS To 800uS
• Release: Continuously Variable 50mS To 1200mS
• Additional Features: A/B Or B/A Signal Routing
• Rack Spaces: 2U
• Power Source: Standard IEC AC Cable
• Width: 19″
• Product Code: B172A
• Please Note:
  • The Attack control on the B17A works a little differently than you may have encountered on other ‘76-style compressors
  • Turning the Attack knob to the left (counter-clockwise) will yield faster attack times; slower times result when turning to the right (clockwise)
  • Turning the Release knob to the left (counter-clockwise) will yield faster release times; slower times result when turning to the right (clockwise)