There is a slight crackling sound when raising the sustain from 0 to 1. The tc electronic FORCEFIELD COMPRESSOR is a compressor pedal designed to improve sound quality, featuring a vacuum tube bypass function. - Brand: tc electronic - Model Name: FORCEFIELD COMPRESSOR - Function: Compressor - Vacuum Tube Bypass: TRUE BYPASS - Input Terminals: INPUT - Output Terminals: OUTPUT 【High-Quality Sound】 The tc electronic FORCEFIELD COMPRESSOR is a high-quality compressor for enriching guitar sounds. By adjusting the sustain and attack, you can freely control the tone. 【Easy-to-Use Controls】 The intuitive knob layout makes it easy to set SUSTAIN, ATTACK, and LEVEL. It is suitable for a wide range of users, from beginners to professionals. 【Reliable Design】 The TRUE BYPASS function ensures that the sound quality is not compromised even when the effect is turned off. The reliable design makes it ideal for live performances. - Brand: tc electronic - Model Name: FORCEFIELD COMPRESSOR - Control Knobs: SUSTAIN, ATTACK, LEVEL - Function: TRUE BYPASS