Earstudio HUD100 - Reviews
Pros: Easy to setup
3 different sound modes
Standard and high-power outputs
Dynamic, detailed but liquid sound
Tiny footprint
Cons: Has a lot of competition at this price point
No dedicated volume or playback controls
Of all the products I’ve reviewed over the last few years, the Earstudio ES100 Bluetooth receiver has been one of the most popular by far. However, when it comes to desktop use, a compact dedicated USB DAC often makes more sense. Enter the Earstudio HUD100, a DAC that has a tiny footprint but plenty of output power and Hi-Res audio quality.

So why do you need an external DAC, instead of just using your laptop or phone’s headphone jack? Well, laptops generally have low-power and low-cost built-in audio solutions. So the default audio quality is not that great and there is a lot of internal electrical interference or noise that can degrade the audio signal. In addition, the Earstudio HUD100 supports higher bitrates (PCM up to 32bit/384kHz) and has native DSD support for up to DSD128.

Radsone Official website: https://www.radsone.com/earstudio

Disclaimer: This sample was provided for the purpose of an honest review. All observations and opinions here are my own based on my experience with the product.

Package and Accessories
The Earstudio HUD100 comes in a simple compact box. Inside the box, you’ll find:
  • Earstudio HUD100
  • 1m USB Type C to A cable
  • 10cm USB Type C to A cable
  • Leatherette travel pouch
  • Owner’s manual
Build and Functionality
Starting with the physical build, the first thing I noticed is how tiny this device is. It’s smaller than a matchbox and in fact, is only 43% volume size compared to the already diminutive ES100MK2. The chassis is aluminium and feels robust despite its mere 21.5g weight.


On the front face of the device are 2 headphone jacks: the first is a standard 3.5mm low-powered (0.914 Vrms) jack which is perfect for sensitive earphones. On the right is a high-power output (2.26 Vrms) that can drive more demanding headphones up to and above 250 Ohm.

Also on the front face is a switch for choosing one of the 3 available sound options. Option 1 is Bypass mode which bypasses any internal sound processing, giving you an unaltered, uncoloured and transparent audio signal. 2 and 3 are DCT and Dynamic modes respectively. DCT produces an analogue-like sound while Dynamic is Radsone’s own processing mode that offers a powerful and balanced sound.

HUD100’s rear face has a USB Type C port plus a firmware update switch. On top of the device is a single small LED that lights up in different colours depending on the current sample rate. For example, when playing a 44.1kHz file, the light glows green and when playing back a DSD128 file, it’s white.

How Does It Work?

All you need to do to start using the HUD100 is plug it into your source device (laptop, smartphone etc.) It’s worth noting that Windows users will need to install the driver to unlock the full functionality. The Windows driver can be downloaded from Radsone’s website. For those who want to use the DAC with their Apple or Android smartphone, you will need a separate adapter which isn’t included in the box.

I’ve seen some people on Head-Fi asking if there is any app or EQ for the HUD100 and the answer to that is no. But, you can simply use the EQ settings on your music software, whether you use Foobar2000, MusicBee, or JRiver etc. On top of that, there are the 3 sound modes which I will cover more in the sound section below.

One thing I dislike about the Earstudio HUD100 is the lack of any physical volume or playback controls. While in general, all laptops have multimedia control functionality via the keyboard, desktop PCs do not. That means unless you have a keyboard with multimedia controls, you have to pick up the mouse to adjust the volume which is hardly convenient.

Internals
According to Radsone, the Earstudio HUD100 has an “elaborate circuit and layout design for best performance in small size”. Furthermore, they claim that this is the first DAC to adopt an ARM Cortex processor to implement their own proprietary algorithms.

The device is built around an AK4377 DAC chip and has a dynamic range of 118dB. Another first for the HUD100 is the MEMS oscillator used as a master audio clock which provides clearer clocks and further reduces jitter. While all that seems rather impressive, it doesn’t mean much unless it actually sounds good. So does it?

Sound
Let’s start with the Bypass mode. True to its namesake, the Bypass mode sounds transparent and uncoloured. What impressed me right away here was the space and air that the music was delivered with.

Firing up Joy Wants Eternity’s “Abide, Moment“, HUD100 sounds wide, deep and has impressive levels of separation. I loved the openness and tonality the song was presented with. Of course, good headphones will make a difference too and for this test, I was using the Beyerdynamic DT990 Pro 250 Ohm with the high-power output. As an aside, the HUD100 has more than enough juice to drive the DT990 Pro’s: I was hovering at around 30-40/100 volume on my Windows PC.

Next up was the DCT mode, playing Outkast’s “In Your Dreams“. The HUD100 delivered the track with good energy and body but didn’t quite match the clean presentation pitched by the Yulong Canary II or its own Bypass mode. Here I matched the HUD100 with the Hifiman Sundara. From the standard output, there was ample volume but to my ears, the bass came across with more depth from the high-power output. Volume levels on my Windows PC were around 24-30/100 (High-Power mode).


Moving onto the Dynamic mode, the bass and midrange are slightly lifted and the sound is filled out with more body. The Earstudio HUD100 in this mode was a great match for Baden Powell’s “Reza“. It’s a track that changes pace and dynamics regularly and the HUD100 flows along with it masterfully. Moreover, it establishes a large, well-defined stage that the various instruments are clearly spread throughout with lots of empty space in between.

For testing the Dynamic mode, I used the DUNU DK-3001 Pro. Plugged into the standard output, the DK-3001 Pro sounds dynamic, full-bodied yet clean and airy and at with Windows volume at around 8-14/100, there was obviously no need to move to the high-power output.

A Note On Source Pairing
While testing the Earstudio HUD100 with my smartphone, I noticed that with my personal setup the power levels were quite limited. This is possibly specific to my older phone (Samsung Galaxy Note 5) and its Micro USB port but I don’t have a compatible OTG cable to test my other phone with its USB Type C port.

Even with fairly sensitive IEMs, I was maxing out the volume when using the standard output and going up to or over 60% from the high-power output. Needless to say, there was nowhere near enough power to drive the DT990 Pro. Even the much less demanding Sundara was too much for this setup. They sounded good but the phone’s volume was maxed out so there was absolutely zero headroom.

Conclusion
Radsone’s Earstudio HUD100 is a unique device that has some unique capabilities. In terms of audio quality, it really sounds fantastic and the 3 various sound modes give some welcome extra versatility.

When plugged into a laptop or PC, the HUD100 can easily drive full-size dynamic and planar headphones with confidence. However, as I found out (at least with my phone) – pairing it with a smartphone may limit you to using easy-to-drive earphones due to power limitations.

So who is the Earstudio HUD100 for? That is the question I kept asking myself during testing. It would obviously be a good choice for people who need portability: someone who spends hours sitting in Starbucks working with a laptop comes to mind.

But for use on a desktop, there are compact DACs like the FiiO K3 which adds a dedicated volume pot, balanced output, bass boost plus line, coax and optical outputs and it costs less. Then there are the dongle DACs like the DragonFlys and the Cozoy TAKT C which has its own onboard volume and playback controls. Furthermore, there are several good DAPs for the same price or less that have the same functionality and Bluetooth.

As I said, the Earstudio HUD100 sounds good – really darn good. It’s compact, well-built and uncomplicated. But it just seems like a weird implementation that will appeal to a small niche audience. If you are one of those people, however, you will be delighted by what you hear.

Specifications
  • Inputs: USB Type C
  • Outputs (3.5mm): Standard 0.914 Vrms / High Power 2.26 Vrms
  • THD+N: Standard -105dB (0.00056%) / High Power -102dB (0.00079%)
  • Dynamic Range: Standard 118dB / High Power 118dB
  • Sample Rates: Up to PCM 32bit 384kHz, DSD128 (DoP)
  • DAC Chip: AK4377
  • Desktop Compatability: Mac OS 10.10 or later / Windows 7 (32/64bit) or later
  • Mobile Compatability: iOS 10.2.2/iPhone 6 or later / Android 6.0 or later
  • Dimensions: 45 x 32 x 8mm
  • Weight: 21.5g
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