Audiobyte HydraVox DAC – Review

I have discovered Audiobyte a long time ago, in 2013. I actually had the pleasure of meeting Nucu Jitariu the founder of both Audiobyte and Rockna, which the big brother of the later. Since then, I have been very impressed of their philosophy, their performance and their products. You can find my previous reviews here and here. My first product from Audiobyte was a high end usb interface. That product was awesome and it provided an instant huge upgrade to a lot of dacs that I have tested at that point in time. After a while, Audiobyte manufactured an upgraded version of the interface which I owned for a good amount of time. The upgrade was incredible and you can read about it here. I also managed to do a small interview with Nucu in my first review, if you are interested.

Since then, they have invested a lot of time into R&D and they came up with some incredible new products. I know that they have been working really hard to release this DAC and I finally have a chance to hear it after years of research. HydraVox is here.


Technical Specifications

You can find all the details here.

  • INPUTS: I2S LVDS (HDMI connector):
  • all sample rates S/PDIF coaxial: up to 192k / DSD64
  • USB: all sample rates
  • RCA single ended: 3.8V (peak)
  • XLR balanced: 3.8V (peak)
  • Headphone out: 9V (peak) T
  • HD+N: -118 dB (0 dB)
  • S/N: -118 dB


The VOX is built around a Xilinx 7-series FPGA device. FPGA = Field Programmable Gate Array – a piece of silicon which allows development of custom hardware. All main functions of the device are specifically made inside the Xilinx device which is updatable, meaning new software will refresh the dac on the hardware level.

Discrete 1-Bit Technology

The architecture of the VOX is pure 1 bit. All incoming sample rates are converted inside to a sample rate equivalent to DSD256/512 (firmware dependent), after which analog conversion is done using current segment technology.

discrete 1 bit technology

Signal Processing

Attaining a high performance 1-bit converter requires extensive digital processing. In order to keep a pristine sound quality, the processing must be done in a resolution higher than the music itself. Using 80 DSP cores running at 200 MHz and 68-bit processing, VOX has enough computing power to preserve the transparency required by the most demanding audiophile. More technical details can be found here [PDF].

signal processing
Phase Correction

A unique feature of the Hydra.VOX is the seamless integration between analog and digital filters in orders to preserve accurate phase of the audio signal. It is well-known that any analog low-pass filter will add a phase distortion input-to-output altering sound quality.

To avoid this from happening, the digital filters inside FPGA are programmed to exhibit a “mirrored” phase response, thus cancelling the phase error from the analog domain. The result is a perfect phase response over the audio band.

Analog Filter/Buffer

While trivial in general applications, the analog buffer stage of the 1-bit DAC is a critical component. Not only must it eliminate the residual noise, but also it should have extreme performance in terms of low distortion and noise floor. In the VOX, the analog buffer stage is realized using low noise bipolar discrete devices.

Headphone Amplifier

The VOX has a 35-bit data path and a very high quality 32-bit volume control, therefore can drive directly any power amplifier. The built-in headphone amplifier is entirely a bipolar discrete design with a max power of 3W/16 ohms.


This DAC also comes with a superb external power supply. I think this is the most intelligent and probably the best power supply I have ever seen or tested. You can read more about it here.

Listening impressions and tests

The tests have been performed with the following gear:

  • Martin Logan ESL-11A Speakers
  • Raimond Audio power amplifier
  • Massdrop THX-789 AAA headphone amp
  • Audeze LCD-2c headphones
  • Quad Era-1 Headphones
  • Soekris 1541 Dac
  • Rockna Wavelight

The tests were done using my PC (Tidal) as source through the USB Input. I am looking forward to hearing hear it with Hydra Hub, which is in the works for the moment.

I like the fact that Audiobyte has an Android application that you can use to control your dac, play with filters and volume. Playing with the filters, I noticed that the sound changes noticeably when switching them, offering some degree of flexiblity of changing the  sound according to your tastes. The Hybrid one was my favorite, presenting a good combination between details, dynamics and clarity. I tested this dac both with my headphones but also on my speaker setup. For now, I didn’t have time to test the headphone output properly.

Sweet Lucy – Cass McCombs, Steve Gun

I was immediately impressed by two things. The guitar plucks are very tactile, but also sweet in a musical manner. The voices were equally impressive because of the clarity & fluidity with which they were reproduced.

Redemption song – Johnny Cash, Joe Strummer

This song presented itself with the same fluidity and musicality as the last one. The vocals are impressively clear and don’t have any grain, leading to a hypnotizing listening experience. The plucks of the guitar had the same sparks of energy with the same precise timing that makes the experience so musical. The guitar strings have a life of their own and you can hear even the micro-details and micro-vibrations. Even the most quiet guitar that is further away is still really alive.

SpoonMan – SoundGarden

So does it rock? Oh, yes it does. Everything was vibrating with life in this song. The punch on the drums was really impressive and the electric guitars had amazingly vibrating and detailed textures.

Rainbow Eyes – Blackmore’s Night

This song shows harshness on a lots of delta sigma dacs. This was not the case with HydraVox. No harshness or sibilance here, just a really opened soundstage, clear and well textured voice and of course sparkly guitars.

MMMBop – Hanson

Another song that would sound a little off(flat, harsh) on a lot of dacs out there. From the start, when the drum kicked in with a really good punch and really detailed extension, I knew this would sound great and it did. Nicely detailed voices and overall a really fun and energetic listen.

The Prophet’s Song – Queen

There is a passage here that I use for tests, the one where you basically have an entire chorus of “Freddies” singing. It sounded as I expected. Every voice presented impressive depth, texture and overall the combination of all voices created a very holographic and impressive listening experience.



The bass is very impressive, packing a very strong punch but also really good extension and detail.


The midrange is really impressive and I would describe it using the following words: clarity/purity, lots of detail, good textures.


The treble is pure and very detail. It lacks the “ringing” harshness found in a lot of delta sigma dacs out there.

Transients & Dynamics

This is another area where this dac excels. It has impressive attack and fast but detailed decays. This translates into a very energetic sound experience with great dynamics but also great micro-dynamics.

Musical Flow

This DAC has really good timing. Combined with the impressive dynamics, it creates a superb listening experience. The musical flows like a clear river but also is full of energy and life.


Yes, this DAC is really detailed. It doesn’t scream the details out to you, they come to you in a very natural way.


The soundstage is natural, the instruments well placed and the overall experience holographic.


I really love Audiobyte’s new product. It manages to have the precision of good delta sigma dacs, but keeping an impressive level of dynamics & energy, a natural musical flow/fluidity without adding harshness on top. I think this DAC is a really good technical achievement and it certainly deserves your attention.  This is the first DAC that made me think of looking to switch from my MSB Analog DAC(which is the oldest component in my system). More on that in the next review.

If you want a more detailed review (both video and written) you can check here. Sandu was actually the one who was able to lend me this unit. Thank you, SoundNews!


  • Impressive bass with really good punch and detail
  • Pure, very detailed and well textured midrange
  • Pure and very detailed treble
  • Incredible transients and dynamics
  • It has a very fluid & musical flow
  • Really good details
  • Good sound-stage
  • Nice design and the menus on the touch screens from the dac and source provided with a good user experience
  • Mobile apps for remote


  • This is not a big thing, but when you use it as a default output device (through USB in Windows), the dac clicks a lot when switching from sound to sound in the same app or different apps.