The Gyraf Audio DIY SSL Compressor, known as the GSSL, is a highly regarded DIY project that allows audio enthusiasts to build their own version of the legendary SSL 4000 series bus compressor. This compressor is renowned for its ability to glue a mix together, providing the punchy and polished sound that has become a staple in professional recording studios. The GSSL project offers a faithful reproduction of this classic compressor, utilizing easily obtainable components and providing detailed guidance for assembly.

Overview

The GSSL Compressor project faithfully replicates the SSL 4000 bus compressor, known for its transparency and ability to enhance the cohesiveness of a mix. The design has been optimized for DIY construction, making it accessible to both novice and experienced audio engineers. With detailed schematics, a comprehensive parts list, and step-by-step instructions, the GSSL is an excellent project for anyone looking to add a professional-quality compressor to their studio setup.

Key Features

•Classic SSL Sound: Emulates the legendary SSL 4000 bus compressor, known for its ability to bring mixes together.

•High-Quality Components: Utilizes readily available and high-quality components to ensure durability and sound quality.

•Detailed Documentation: Includes thorough schematics, a parts list, and step-by-step assembly instructions.

•User-Friendly Design: Designed for ease of construction with PCB-mounted components and clear layout guidelines.

•Versatile Controls: Features controls for threshold, ratio, attack, release, and make-up gain, providing comprehensive dynamic control.

Building the GSSL Compressor

Preparation:

1. Component Verification: Ensure all components, especially resistors, capacitors, and ICs, are correctly valued and in good condition before starting assembly.

2. PCB Layout: Follow the provided PCB layout files, printed to the exact scale for accurate and efficient construction.

3. Soldering Technique: Use proper soldering techniques to avoid shorts and ensure solid connections.

Assembly Tips:

•Transformer Selection: Choose the appropriate power transformer based on the voltage requirements specified in the documentation.

•IC Placement: Pay close attention to the orientation of integrated circuits to avoid damage and ensure proper operation.

•Grounding: Proper grounding is crucial to avoid noise and hum. Ensure all grounding points are securely connected.

Adjustment and Calibration

Initial Setup:

•Power Supply Check: Verify that the power supply outputs the correct voltages before connecting to the main PCB.

•Component Placement: Double-check the placement of all components against the schematic to ensure accuracy.

Calibration Steps:

•Threshold Calibration: Adjust the threshold control to set the level at which compression begins.

•Ratio Calibration: Set the compression ratio to determine the degree of gain reduction.

•Attack and Release Calibration: Fine-tune the attack and release times to control the response of the compressor to transients.

•Make-Up Gain: Adjust the make-up gain to compensate for the gain reduction and achieve the desired output level.

Troubleshooting

Common issues may include:

•Incorrect component values or placements leading to malfunction.

•Soldering errors causing shorts or poor connections.

•Power supply issues due to incorrect transformer wiring or insufficient heat sinking.

Resources:

•Online Forums: Join forums like GroupDIY for community support and troubleshooting advice.

•Detailed Guides: Follow the detailed assembly and calibration guides provided by Gyraf Audio.

Enhancements and Customizations

Sidechain Filter:

•Add a sidechain filter to the compressor to achieve more versatile compression characteristics, particularly useful for controlling low-end frequencies.

Stereo Linking:

•Implement a stereo linking option to use the compressor in stereo applications, ensuring consistent compression across both channels.

Metering Options:

•Customize the metering section with VU or LED meters to provide visual feedback of the gain reduction and output levels.

Conclusion

The Gyraf Audio DIY SSL Compressor is a fantastic project for audio enthusiasts looking to capture the classic SSL sound in their recordings. With its detailed documentation, high-quality components, and user-friendly design, the GSSL offers both a rewarding building experience and a professional-grade compressor. Whether you are an experienced DIYer or new to audio equipment construction, the GSSL is an excellent addition to any studio, providing the punch and polish that have made the SSL 4000 series compressors legendary in the world of audio production.

See the documentation tab for build docs.

Additional Resources

•Gyraf Audio DIY SSL Compressor Page

•GroupDIY Forum

Explore these resources for more detailed instructions, schematics, and community support as you embark on building your own GSSL compressor.

*Analog Classics does NOT provide build support for this project.