DSD & Resonessence Labs’ Herus

Editor’s Note: When Mr. T reviewed the Resonessence Labs Concero HP last year (review here), he was thoroughly impressed by its robust build and superlative sound quality, along with Resonessence’s impressive technical service attributes. However, the Concero HP, being the size of a removable optical drive, was merely a transportable device, rather than a truly portable one. AnakChan gives us a pithy overview of the Herus, the Canadian firm’s smallest device yet.

The tiny Resonessence Labs Herus.
The tiny Resonessence Labs Herus.

Last year in October, Resonessence Labs released a small portable DAC/Amp called the Herus,  a device smaller and shorter than two stacked packs of gum.

Despite its diminutive size, the Herus is based on the new ESSTech ES9010-2M DAC, giving it considerable decoding ability, up to 24-bit, 352.8 kHz DXD resolution in PCM mode, and up to 1-bit, 5.6 MHz for double DSD rates.

In addition to decoding from the PC, the Herus‘ low current draw also gives it the ability to work directly off any iDevice (and most Android devices as well) without the need for an external battery (Apple sets the limit to 100 mA over USB), allowing it to be a truly portable device. Having DSD at your fingertips has never been so convenient.


Minimalism is the theme for the Herus — there are no buttons, no external volume control, and merely takes in a USB Type B input on one end, and a 1/4” single-ended output on the other end. It lights up red when it’s first connected to a transport and subsequently changes blue when there’s sync.

As there’s no physical volume control, it’s done through software instead. I must admit I’m still not used to software volume control (actually it’s a software-controlled abstraction of on-board hardware-controlled 32-bit digital volume control) as whilst writing this review, I accidentally scrolled to max volume on my Audirvana+ from my Macbook Air touchpad and blew my ears out. That hurt.

Similarly on the iPad, the volume touch is very sensitive. Since this the Herus is very output capable (2.4 Vrms, 6.8V peak to peak) one has to be very careful with the volume control.

As a former Herus user, our shotgunshane also felt the digital volume control of the Herus needed to be paired with an app that delegated more volume steps to the slider, such as CanOpener (review here).

The Herus plays nice with the iPad (and any other iOS device; shotgunshane used it with the iPhone). However, beware of the volume control and decreased battery life.
The Herus plays nice with the iPad (and any other iOS device; for example, shotgunshane used it with the iPhone). However, beware of the limited 16-step onboard volume control and decreased battery life.


Although I’ve had the Herus since last October, I have to admit that I didn’t focus on it much. I used it primarily on my iPad and the sound didn’t thrill me as much as I had hoped.

In fact, it was only recently in the past two months when I purchased the Onkyo HF Player with the DSD native plug-in that I started to appreciate the magic of the Herus — as such, DSD will be the focus of this review.

Of all the devices I have that support DSD either natively or through real-time conversion to PCM, none had such a great difference between its presentation of PCM versus DSD as has had the Herus.

For most of my other devices, including the first generation Invicta (Resonessence Labs’ desktop flagship), the difference between PCM and DSD was one of incremental improvement for smoothness, along with minor refinements here and there, contributing to a more pleasing sound overall.

The Herus with its (much) bigger brother, the Invicta.
The Herus with its (much) bigger brother, the Invicta.

With the Herus, however, the switch to DSD felt like I was listening to a completely different DAC/Amp altogether — there was more treble sparkle, a more impactful thump in the bass, and more distinctive instrument separation — just overall “richer” and cleaner experience.

To experiment a little further, I did comparisons of the Herus with the following setups :

  • Apple MacBook Air with Audirvana+ set to:
  1. Down convert DSD to PCM
  2. Play DSD natively
  • Apple iPad with:
  1. Apple’s Music Player playing ALAC
  2. Onkyo Music Player playing ALAC
  3. Onkyo Music Player playing DSD natively

In all cases, DSD native decisively triumphed over its ALAC counterparts. For my ears, Herus‘ presentation in DSD native wasn’t far short of the Astell&Kern AK240 playing the very same DSD track.


For DSD play, the Herus is truly demonstrating its strength and its ability to join the ranks of some of the other high end DAPs that have DSD native support — but at a fraction of the cost.

For more information about the Resonessence Labs Herus, please visit: http://resonessencelabs.com/herus/

About AnakChan
I’m a technologist by profession and have been an audio enthusiast for over 13 years — only more recently have I come out to become more active in the audio community. I very much enjoy reviewing, writing, and sharing my impressions with fellow enthusiasts.
(Author Website)

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