DENAFRIPS HERMES 15th is a digital-to-digital converter, also known as a DDC, designed to be placed between a digital source and a DAC. Its task is to receive the signal from a computer, streamer, CD transport or other compatible source, process it and send it back in digital format to the converter. This provides a central connection point for digital audio systems requiring greater flexibility between inputs and outputs.

The HERMES 15th uses a proprietary FPGA DSP architecture, a FIFO buffer system and dual temperature-compensated OCXO oscillators. The combination of these elements is designed to manage the signal with timing precision and stability. Galvanic isolation of the digital inputs via opto-couplers also helps separate the circuits and limit interference transfer between the different sections.

DDC for digital sources and DACs

HERMES 15th can be used when you want to connect a source equipped with a particular digital output to a DAC featuring a different input. The equipment includes USB, coaxial, optical and AES/EBU inputs, while the outputs include coaxial, optical, AES/EBU and I²S. Multiple configuration options are therefore available, depending on the connections present on the system components.

• USB input: USB 2.0 Type B, for connection to a computer or compatible USB source.
• Coaxial input: Coax SPDIF interface via RCA connector.
• Optical input: one TOSLink input.
• AES/EBU input: one AES/EBU digital input.
• External clock input: 75 Ω BNC connector.
• Digital outputs: coaxial, optical, two AES/EBU, I²S over HDMI according to the LVDS standard and I²S over RJ45 according to the LVCMOS standard.

The presence of two AES/EBU outputs also allows dual AES configurations to be managed when the connected DAC provides this type of interface. I²S outputs are available both on HDMI and RJ45; as these are specific standards, compatibility must be checked in relation to the DAC used and its pinout or I²S configuration.

FPGA processing, FIFO buffer and OCXO clock

At the heart of the device is a proprietary solution based on FPGA DSP. The digital signal is managed through a FIFO buffer and a reclocking system with an internal reference. The buffer organizes the data stream before transmission to the outputs, while reclocking uses the time base generated by the internal oscillators.

HERMES 15th integrates two temperature-compensated femtosecond OCXO clocks. The stated frequencies are 45.1548 MHz and 49.152 MHz. Temperature compensation is used to keep the clock reference stable as operating conditions vary. Together with the FPGA architecture and input isolation, this section is intended to ensure accurate management of digital-signal timing and reduce jitter and phase noise.

The 75 Ω BNC external clock input expands the integration possibilities in systems using an external synchronization reference. However, the actual operation of this connection depends on the characteristics and connections of the rest of the system.

USB, PCM and DSD support

The USB connection uses a proprietary USB Audio solution based on an STM32F446 microcontroller. A licensed Thesycon USB driver is provided for Windows computers, while operation on Mac and Linux is indicated as driverless. This allows the computer platform to be selected according to the available source, while maintaining the connection through the USB Type B input.

The device supports 24-bit PCM signals with sampling frequencies of 44.1, 48, 88.2, 96, 176.4 and 192 kHz on the specified inputs and outputs. Through the USB input, the stated frequency reaches up to 768 kHz. The I²S output supports frequencies up to 384 kHz. Before installation, it is advisable to verify that the source, software and DAC can handle the desired format.

For coaxial, AES/EBU and optical connections, DSD64 support via DoP is specified. Through the USB input and I²S output, support reaches up to DSD512. The available modes therefore depend on the type of input used and the output selected: not all formats are specified for every combination of connections.

Linear power supply and isolation

The power-supply section is based on an 80 VA shielded O-core transformer, wound with UPOCC copper. Eight independent ultra-low-noise linear regulators are present, intended to provide separate and stable power to the different internal sections. The design specifies a rated power of 100 W and stable operation at 80 W; the indicated power consumption is instead equal to or less than 20 W.

Galvanic isolation of the digital inputs via opto-couplers helps electrically separate the interfaces. This design choice is combined with digital-domain signal processing through FPGA DSP and the FIFO buffer. The sections together do not change the nature of the product: HERMES 15th remains a DDC and is not a DAC, so it must be connected to a digital-to-analog converter for listening through an analog system.

Construction and connections

The chassis is made entirely of aluminum, with CNC machining, anodizing and a brushed finish. The aluminum construction is completed by a gold-plated BNC connector and a rhodium-plated power socket. The stated color finish is Black Silver. These elements define a structure designed to house the processing section, linear power supply and connection panel in an orderly manner.

To configure HERMES 15th, first identify the source’s digital output and the input available on the DAC. A USB source can be connected to the DDC’s USB input, while players or transports with SPDIF, optical or AES/EBU outputs can use the respective interfaces. On the DAC side, select the compatible output: coaxial, optical, AES/EBU or I²S, checking in the latter case the standard supported by the receiving device.

Main data and intended use

HERMES 15th is intended for those who want to organize a digital system with multiple sources or use an output interface different from the one directly available on the source. Support for USB, SPDIF, optical, AES/EBU and I²S makes it suitable for configurations with different digital components, while high-resolution format management keeps PCM available up to the stated values and DSD according to the connection used.

• Type: digital-to-digital converter DDC.
• Processing: proprietary FPGA DSP with FIFO buffer and reclocking.
• Clock: dual temperature-compensated femtosecond OCXO.
• Power supply: 100-240 VAC, 50/60 Hz.
• Consumption: ≤20 W.
• Stated warranty: 12 months.

Thanks to its combination of multiple connections, OCXO clock, galvanic isolation, linear power supply and aluminum chassis, the DENAFRIPS HERMES 15th is intended as a digital interfacing center for audio systems based on external DACs.

Main features

• Product type: Digital-to-digital converter (DDC)
• Power consumption: ≤20 W
• AES/EBU input: 1 input
• AES/EBU output: 2 outputs
• BNC connector: Gold-plated
• Buffering: FIFO buffer

Technical specifications

Product type	Digital-to-digital converter (DDC)
Power consumption	≤20 W
AES/EBU input	1 input
AES/EBU output	2 outputs
BNC connector	Gold-plated
Buffering	FIFO buffer
Chassis material	Aluminum
Clock frequency	45.1548 MHz
Clock frequency	49.152 MHz
Oscillator	OCXO
Clock type	Dual temperature-compensated femtosecond OCXO clocks
Coax input	Coax SPDIF via RCA
Digital inputs	USB / coaxial / optical / AES
Digital outputs	Coaxial / optical / AES / I²S (HDMI)
Digital signal processing	Proprietary FPGA DSP architecture
DSD on Coax/AES/Opt	DSD64 via DoP
DSP architecture	Proprietary FPGA DSP
External clock input	BNC 75Ω
Buffer and reclocking	FIFO buffer and reclocking with internal crystal
Galvanic isolation	Via opto-coupler
I²S HDMI output	LVDS standard
I²S RJ45 output	LVCMOS standard
Frequency via I²S	Up to 384 kHz
Input isolation	Digital input interfaces with optical isolation
Linear regulators	Eight independent ultra-low-noise linear regulators
Mac and Linux support	Driverless
PCM resolution	24 bit
PCM frequencies	44.1; 48; 88.2; 96; 176.4; 192 kHz
Power supply	100-240VAC, 50/60Hz

Technical details

The listed specifications help compare the product’s configuration, compatibility and performance.

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Frequently asked questions

What is the DENAFRIPS HERMES 15th?

It is a digital-to-digital converter, or DDC, which receives a signal from a digital source, processes it and sends it to a DAC through a compatible digital output.

Which digital inputs are available?

There are USB 2.0 Type B, coaxial SPDIF via RCA, one TOSLink input, one AES/EBU input and a 75 Ω BNC external clock input.

Which outputs can be used with a DAC?

The outputs include coaxial, optical, two AES/EBU, I²S over HDMI according to the LVDS standard and I²S over RJ45 according to the LVCMOS standard.

Which formats does it support via USB?

Via USB it supports PCM up to 24 bit and frequencies up to 768 kHz, as well as DSD up to DSD512 on the I²S output. Final compatibility also depends on the source and DAC.

Are drivers required to use the USB input?

A licensed Thesycon USB driver is provided for Windows. Operation on Mac and Linux is indicated as driverless.