The Holo Audio RED is a versatile audio device designed to function as both a Digital to Digital Converter (DDC) and an Audio Network Bridge. This document provides comprehensive guidance on its installation, configuration, and various operational modes.

Function Description

At its core, the Holo Audio RED serves two primary functions:

Digital to Digital Converter (DDC): In this mode, the RED acts as a high-quality interface, converting digital audio signals from a USB input to various other digital output formats, including I2S and S/PDIF (Coaxial, Optical, AES-EBU). This allows users to connect a computer or other USB audio source to a DAC that may not have a direct USB input or to improve the quality of the digital signal before it reaches the DAC. The internal architecture of the RED is built with multiple sets of ultra-low noise linear regulated power supplies, high-quality clocks, USB signal processors, and a dedicated USB DDC, all contributing to a clean and precise digital audio output.
Audio Network Bridge: When configured as a network bridge, the RED transforms into a streaming endpoint, enabling it to receive audio data over a local area network (LAN) and output it to a connected DAC. This functionality is particularly useful for integrating the RED into a home audio network, allowing for streaming from various sources without a direct USB connection to the playback device. The device supports a wide array of popular audio services, including NAA HQPlayer, Roon Bridge, UPnP, AirPlay, Squeezelite, Scream*, Spotify Connect, and Tidal Connect. All these services can be activated simultaneously, offering significant flexibility in how users access and stream their audio content. The Scream feature, which acts as a virtual network sound card for Microsoft Windows, is a unique offering, though it is limited to standalone mode operation.

The internal design of the RED emphasizes signal integrity and power purity. It incorporates a Raspberry Pi CM4 for processing network audio and managing the RedOS software, ensuring robust and reliable operation. The careful separation and regulation of power supplies for different internal components, along with precision clocks, are critical for minimizing noise and jitter, which are common issues in digital audio systems.

Usage Features

The Holo Audio RED offers flexible setup options to cater to different user needs:

Quick Start Guide: The manual provides a straightforward quick start guide for initial setup, covering unpacking, MicroSD card insertion (pre-loaded with RedOS software), and power connection.
DDC Mode Setup: To use the RED as a DDC, users need to power off the device, unplug the LAN cable, connect a USB cable from the Roon Core (or other USB audio source) to the RED's USB-IN, and then connect an HDMI cable from the RED to their Holo DAC. After powering on, the RED should be discoverable in Roon Core's Audio Setup, allowing users to enable it and begin playing music.
Streaming Bridge Mode Setup: For streaming bridge functionality, the process involves powering off the RED, unplugging the USB cable, connecting a LAN cable to the RED, and an HDMI cable to the Holo DAC. The device will then act as a network bridge, with its services accessible via its IP address through a web browser interface.
IP Address Discovery: The manual guides users on how to find the RED's IP address on their network, which is essential for accessing the web-browser interface to enable/disable audio services and configure settings. It recommends using network scanner tools like "IP Scanner" or "AngryIP" to locate the device, especially if it's not automatically detected by Roon.
I2S Output Configuration: A key feature for audiophiles is the configurable I2S output. The RED allows users to adjust the I2S output line sequence using DIP switches located at the bottom of the chassis. Four different I2S configurations (Holo Audio, Alt 1, Alt 2, Alt 3) are available, ensuring compatibility with a wide range of DACs that utilize the I2S interface. Additionally, DIP switches control the I2S_DSD_ON enable and the I2S_MCLK frequency, offering granular control over the digital signal characteristics.
Front Panel Indicator: The front panel features an LED status indicator. A steady green light signifies power, while a flashing red light indicates load activity, which is normal and varies with the usage load.
Connectivity: The rear panel of the RED is equipped with a comprehensive set of interfaces: optical fiber, system TF card holder, I2S (HDMI), AES, coaxial 1, coaxial 2, USB input, USB output, network port (ETH), and AC power input. This extensive connectivity ensures the RED can integrate seamlessly into various audio setups.

Maintenance Features

The manual emphasizes critical precautions to ensure the longevity and proper functioning of the device:

TF Card Handling: Users are explicitly warned against hot-plugging the TF card. It is crucial to turn off the power before inserting or removing the TF card to prevent potential damage to the card and the internal chip. This highlights the importance of careful handling of the system's core software storage.
I2S Interface Note: While the I2S interface uses an HDMI physical connector, the manual clarifies that it transmits I2S electrical signals, not conventional HDMI audio and video signals. This distinction is important for users to understand when connecting the RED to a DAC, ensuring they use it for its intended purpose and avoid misinterpretations.
Coaxial Output Caution: The manual advises that Coaxial 1 and Coaxial 2 outputs cannot be short-circuited, a standard precaution for digital audio outputs to prevent damage.
RedOS Settings: Users are advised not to change settings in RedOS unless they are knowledgeable about the implications. This suggests that the default configuration is optimized for most users, and unnecessary modifications could lead to operational issues. The USB redirector, for instance, is pre-configured and typically does not require changes.
Power Input Configuration: The device's power input is configurable, with details provided on the bottom label of the machine. This allows users to ensure they are using the correct power settings for their region (e.g., 220~230V or 100~115V), which is a fundamental aspect of device maintenance and safety.

Overall, the Holo Audio RED is presented as a sophisticated and flexible device for enhancing digital audio playback, designed with both performance and user-friendliness in mind, provided that the recommended precautions and setup procedures are followed.

Holo audio RED - I2 S Layout

Table of Contents