The S3 let you keep your 500 series module where you want to. Whether you are producing muisic in your studio or recording a live performance, your project always goes smoother when you've tailored your workflow to your style. The S3 makes it easy to combine world-class 500 series mic preamps, EQs,compressors and more in one convenient desktop/porable chassis. With three empty slots, it is perfect for creating a personalized selection of processors for your specific needs.