Avid Pro Tools HDX Core PCIe CardPro Tools HD software not included. Pro Tools HDX is the new generation of DSP based PCIe interface card for Pro Tools, replacing the legacy Core and Accel PCIe cards. With one card, you can mix up to 256 voices. If you need more tracks and power, you can expand your Pro Tools HDX system with up to three cards. With two cards, you can mix up to 512 voices, and with three cards, you can have up to 768 voices, eliminating the need for an expansion