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Hydra X+ - Reference USB interface

Either if you love your current setup and don't want to change your DAC, or just want to upgrade your current USB interface, the Hydra X+ is the perfect way to add (or improve) computer based playback on your system.

The Hydra X+(treme) was designed as the ultimate USB interface in terms of both objective and subjective performance. Built around the latest generation of FPGA technology, the goal of the design was to produce stunning sound and to offer the highest definition available for a commercial product.

To achieve this goals some key factors are defining the Hydra design :

The ultra high-speed USB interface capable of very high audio sample rates. The Hydra is equipped with a modern ARM processor for resolving USB transactions.

The isolation between noisy PC environment and the audio chain. The USB isolation for audio devices is nothing but tricky. If you choose to use USB isolators, then sample rate will become limited, which is not an option. If you choose to isolate the output, you are adding significant amounts of jitter to the signal. By using a clever circuit topology, the Hydra design avoids these two bottlenecks. The isolation is placed between the ARM processor and the FPGA audio core, therefore not limiting the bandwidth. Being before the clocks, it's jitter contribution becomes irrelevant. See the Hydra X+ technical paper for more details.

The Spartan6 FPGA is the heart of the Hydra. This advanced programmable circuit is offering a bit-transparent processing and signal conditioning to S/PDIF, AES/EBU, Toslink and I2S outputs. It also gives the ability of the Hydra to output raw dsd audio streams.

The clocks Unlike other products which only specify "low jitter clocks", we are saying the exact type of what we're using: it's the CCHD-950/957 type from Crystek, one of 45.1584 Mhz and one of 49.152 Mhz. You can check real graphs of these ultra-low phase noise clocks here. The clocks are system masters. In order to remove any jitter induced by the FPGA circuit itself, special retiming is applied just before the Hydra outputs.

The battery A low impedance, LiPo-nano technology, provide to the system the cleanest power supply needed for pristine audio performance. All sensitive circuitry like the clocks, FPGA and retiming circuitry benefit from battery power. The USB port and external (optional) are alternative options for powering the system, but everything was primarily designed to work with clean battery power.

Careful PCB layout is often neglected in the rush of getting a product quickly into the market. The Hydra X+ design time took many months until everything came close to perfection, until the shortest routing paths, the best decoupling places, the less interference and crosstalk placement for the components are found.

Owner's Manual


USB drivers





Product images

Technical specifications:

  • Power consumption : 0.7 W
  • Battery charge time : 9h (some versions 2h)
  • Battery playback : 45h (some versions 10h)
  • Dimensions : 125 x 105 x 60 mm
  • Weight : aprox. 0.8 kg
  • USB receptacle, type B high-speed
  • S/PDIF, 75 ohm coaxial
  • AES/EBU, 110 ohm XLR
  • BNC 75 ohms
  • I2S over HDMI (LVDS)
  • 44.1 KHz
  • 48 KHz
  • 88.2 KHz
  • 96 KHz
  • 176.4 KHz
  • 192 KHz
  • 352.8 KHz
  • 384 KHz
  • 2.8 MHz (DSD64) - DoP, native
  • 5.6 MHz (DSD128) - DoP, native
  • 11.2 MHz (DSD256) - native (via ASIO)
  • 22.5 MHz (DSD512) - native (via ASIO)
  • 32 bit over I2S output
  • 24 bit over S/PDIF, AES/EBU, Toslink
  • Native MacOS 10.6 and later
  • Native Linux with UAC2 compliant kernel
  • ASIO, WASAPI, KS, DS drivers for Win XP to W8 32/64 bit
  • Recommended players : Foobar2000, Audirvana Plus, Jriver etc.

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