The NE4400D is part of Ashly's Protea™ NE series of networked processors. The "D" in the model name specifies the AES3 (also known as AES/EBU) digital input option, which comes pre-installed, occupying one of the four expansion bays. This allows the unit to receive high-quality digital audio signals directly, alongside its standard four balanced analog line-level inputs. The core of the device is a powerful 32-bit floating-point SHARC processor array that provides an extensive library of DSP functions, all controllable via Ethernet and Ashly's Protea NE Software.