Gyraf G9 Tube Mic Pre-Amp PCB Set

The Gyraf Audio G9 Tube Mic Preamp is an exceptional DIY project designed for audio enthusiasts who want to create a high-quality, versatile microphone preamplifier. Inspired by classic tube preamp designs, the G9 offers rich, warm sound characteristics and robust performance, making it an excellent choice for both professional and home studios. This guide provides an in-depth look at the features, assembly process, and performance of the G9, ensuring a rewarding building experience and outstanding audio results.

Overview

The G9 Tube Mic Preamp is based on a dual-channel design, each featuring two ECC88/6922 tubes. It combines the best of vintage tube technology with modern components to deliver a preamp that is both reliable and sonically superior. The project includes detailed schematics, a comprehensive parts list, and step-by-step assembly instructions, making it accessible to both novice and experienced DIYers.

Key Features

•Classic Tube Sound: Utilizes ECC88/6922 tubes for warm, rich sound.

•Dual-Channel Design: Two independent channels for versatile recording applications.

•High-Quality Components: Uses readily available, high-quality components to ensure durability and performance.

•Detailed Documentation: Comprehensive schematics, parts list, and step-by-step assembly instructions.

•Versatile Inputs: Supports both microphone and line-level inputs with switchable phantom power.

•Output Options: Balanced XLR outputs for professional connectivity.

Building the G9 Preamp

Preparation:

1. Component Verification: Ensure all components are correctly valued and in good condition before starting the assembly.

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

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

Assembly Tips:

•Tube Mounting: Pay close attention to the orientation and mounting of the ECC88/6922 tubes to avoid damage and ensure proper operation.

•Transformer Wiring: Follow the provided wiring instructions for the input and output transformers to ensure optimal signal transfer.

•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:

•Bias Adjustment: Adjust the bias of the tubes to achieve the desired operating point and minimize distortion.

•Gain Setting: Set the gain control to match the input signal level and achieve the desired output level.

•Frequency Response: Test the preamp’s frequency response and make any necessary adjustments to the circuitry to achieve the desired sound profile.

•Noise Reduction: Ensure proper grounding and shielding to minimize noise and hum.

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.

See the documentation tab for build docs.

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.

Analog Classics does NOT provide build support for this project.