The Keeley Electronics 4 Knob Compressor rocks. Compression has long been a studio and stage essential for pro guitarists, and Robert Keeley is making some of the best-sounding compressors on the market. What’s his secret? Robert uses only the highest-quality components, resulting in a stompbox that preserves your guitar’s natural tone, while juicing clarity and balancing out the strings. With the 4 Knob, you’re getting studio-grade compression in a stompbox form factor. If you like your guitar sound up front and transparent, you need the Keeley 4 Knob Compressor in your rig.