The HDP-4, is a stereo digital processor than can be installed between preamp and amplifier or more directly used as a preamp/processor. The new HDP-4 has both analog and hi-res digital inputs offering RCA, XLR analog inputs and toslink, coax, BNC, AES/EBU digital inputs. All digital inputs will receive 44.1kHz and 48kHz signals and multiples there of up to 176.4kHz and 192kHz, respectively. There is also an optional USB input module.

The HDP-4 comes with many output options standard like SPDIF on true 75 ohm BNC connectors, balanced analog outputs, with another digital output configured as a DSP Input Pass-Through for connecting selected inputs for further processing. The balanced analog outputs as standard is a particularly nice improvement over the HDP-3

The HDP-4 signal path consists of audiophile quality components. A highly regulated analog power supply delivers extremely low measured distortion and provides a background that is so silent that all you can hear is the music.