Gyraf 1176 Compressor PCB Set

Gyraf Audio DIY 1176LN Compressor: A Comprehensive Guide

The Gyraf Audio DIY 1176LN Compressor offers audio enthusiasts a chance to build their own version of the classic UREI 1176LN rev#F. This project adapts the original design to accommodate readily available components, ensuring that anyone can recreate this legendary FET compressor. With detailed schematics, a comprehensive parts list, and step-by-step instructions, this guide will walk you through the entire process of constructing your very own 1176LN compressor.

Overview

The G1176 is a faithful adaptation of the original UREI 1176LN rev#F, utilizing standard European transistors, a Lundall output transformer, and rotary switches for easier enclosure layout. This project is perfect for DIY enthusiasts looking to dive into the world of audio compression with a hands-on approach.

Key Features

• Classic FET Compression: Emulates the sound of the original UREI 1176LN rev#F.
• Standard Components: Utilizes readily available European transistors and other components.
• Detailed Documentation: Includes a complete parts list, schematics, and adjustment procedures.
• Community Support: Access to forums and resources for troubleshooting and enhancements.

Building the Unit

Preparation:

1. Component Verification: Ensure all components, especially resistors, are correctly valued before soldering.
2. Heat Sink Usage: Apply a small heat sink to the 7824 voltage regulator to prevent overheating.
3. PCB Inspection: Thoroughly check the PCB for shorts and solder blobs before powering up.

Assembly Tips:

• Pin Compatibility: Verify that NTE substitutes for semiconductors are pin-compatible.
• Transistor Placement: Be cautious with transistor placement as they are sensitive to incorrect mounting.
• Grounding: Properly connect the center tap of the 2x24V transformer to ground and ensure the chassis ground is connected at the input XLR(F) connector.

Adjustment Procedures

Q Bias:

• Bypass the unit, input a signal, and adjust the trimmer until a 1dB level drop is achieved.

Distortion Trim:

• Set the unit gain to unity and adjust the trimmer for minimum distortion.

GR Meter Zero:

• With no input signal, adjust the meter to read 0dBVU in GR mode.

GR Meter Tracking:

• Calibrate the gain reduction meter by adjusting the trimmer to reflect accurate dBVU readings during signal input and output comparisons.

Troubleshooting

Common issues include:

• Incorrect component values or placements.
• Overheating due to insufficient heat sinking.
• Short circuits on the PCB.

Resources:

• Online Forums: Access community forums for additional support and troubleshooting tips.
• Adjustment Guides: Refer to simplified adjustment procedures for easy calibration.

Enhancements and Customizations

SLAM Mode:

• Popularly requested, the SLAM or NUKE mode can be incorporated for more aggressive compression settings.

Input Transformer Option:

• An optional LL1540 input transformer can be added to enhance sound quality, although it’s not part of the original design.

Conclusion

Building the Gyraf Audio DIY 1176LN compressor is a rewarding project for audio enthusiasts, offering a hands-on approach to understanding and replicating one of the most iconic FET compressors in audio history. With detailed documentation, community support, and the flexibility to customize, this project ensures both a learning experience and a high-quality audio tool.

See the documentation tab for build docs.

Additional Resources

• Gyraf Audio DIY 1176LN Page
• GroupDIY Forum
• Original UREI 1176LN Manual (PDF)

Explore these resources for more detailed instructions, troubleshooting tips, and community support as you embark on building your own 1176LN compressor.

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