Peavey PC4-XLa Software Upgrade Version of PC4-X and PC4-XL offers enhanced features for precise audio control and optimization. With additional equalization and limiter options, you can tailor the sound output to suit your specific needs. The improved user interface simplifies access to various functions, including the ability to store and recall up to 50 complete setups with custom labels. The security lock feature enhances control and prevents unauthorized changes to your configurations.