Radsone Earstudio ES100 mk2 : Excellent device, due an update


What a music lover (including audiophiles) will do when they buy a premium phone with excellent cameras, bezel less displays and extremely powerful processors which misses out on 3.5mm connectivity? These mobile brands are smart. They have their own wireless earphones and they sell in millions but the problem comes when an audiophiles vying for sound quality gets tired of the new toy feel and wants to enjoy the music in a more refined and detailed state. There are other options like DAPs and USB DACs but a device that can work as a USB DAC and wireless DAC makes more sense.

Some brands like Fiio and Radsone figured it out couple of years ago. They came up with Bluetooth DAC/Amps which can be used with mobile phones both wired and wirelessly.

Radsone’s ES100 MK2 is one of those gems. Hailing from South Korea Radsone has made a huge impact with their ES100 Bluetooth dac/amp. It doesn’t have any color options but Midnight blue and is priced in the range of $75 to $99 depending upon where you buy it from.

I am working on a handful of USB DAC/Amps and already have the Shanling UP4 for comparing the ES100 MK2 wirelessly.

Get one for yourself from here:-


The ES100 mk2 comes in a tiny box. It looks cute and makes sense as there isn’t much inside the box except a short micro USB cable and a QSG. The device itself is well protected with soft sponge from every direction. It is hard to expect anything from a wireless device, even when it can be used in wired mode with mobile phones there is no cable in the box that enables that. All we get is a small micro USB cable to charge the device and maybe connect with the PC.
There is a built in clip to hold on to cloths, soo.. nothing else in the box.


The ES100 MK2 has a dimension of just 1/2/0.5 inch and weights at just 20g. It feels sturdy and solid in the hand. Body is made out of plastic, other like BTR5 use more premium material like Glass but the ES100 doesn’t feel cheap but frugal. Strangely the clip on the back is made out of metal. Good news is it has scratch resistant coating on it which should protect it from minor scratches. Unlike any other USB DAC/Amp the ES100 mk2 has analog volume controls, play pause, forward and back switches which work perfectly in both wired and wireless modes. Sadly the microphone placed just aside the volume buttons doesn’t work in USB mode. The switches have very good feedback. Both the 2.5mm and 3.5mm sockets are placed on either side. We have a blink LED to indicate the states of connectivity. It blinks blue when turned on then green and red while in pairing mode and green again when paired and red when turned off.

Connecting it is simple. Pair it with mobile phones with Bluetooth with usual pairing routine. Hold the power on button for 2 seconds to turn it on. Hold the back key for two seconds to enter pairing mode again if you want to connect it with two devices. Use a Micro to Type C USB cable to connect the device in USB mode.

The Class 1 USB helps the ES100 mk2 with wider compatibility and it doesn’t need any drivers to work with Windows PCs.


ES100 MK2’s AK4375a DAC chip is not the best in the market but the good thing is it has two of them for a true balanced output. Thankfully I am aware of what Radsone can extract from their devices with excellent implementation. Premium components like jitter clock and dual amplifiers bring more clarity and resolution. It supports high quality wireless codec like LDAC and aptX-HD for optimal sound quality.

Equipped with CSR8675 the ES100 MK2 is compatible with BT 5.0 and supports 24bit Bluetooth encoding.

The ES100 is equipped with both 3.5mm and 2.5mm balanced output. The one on the left side along with volume buttons is for the single ended use with a power of 1.1vrms which turns out at around 137.5mw with a SNR value of 109 DB and should be plenty for most of the earphone in the market. The one on right along with forward and back buttons is for 2.5mm balanced output with a power output of 2.2vrms along with a SNR value of 110 DB which is good enough for power hungry earphones and headphones. The ES100 mk2 can easily drive most of the headphones except those who are power hungry.

The decoding power of the ES100 is not excellent as it is capped at 24bit and 48khz.


It has very powerful app with a lot of controls, you can control nearly everything. A lot to explain.. soo..


Unlike HUD100 mk2 the ES100 mk2 comes with a built in battery which is good for at least 9-12 hours of wireless usage irrespective of the output you are using. If used as an USB DAC the battery life is much longer as it can sip power from the mobile phone.

I found the battery life to be more than enough for day to day usage. I was mixing it up (wired and wireless) and the battery was fairly good as I only had to charge the ES100mk2 twice in 8 days with usage of at least 70 hrs.


ES100 Mk2 is a very interesting DAC. It does not have an upper tier DAC chip but is much better at revealing details than the more expensive and fancy Hip DAC. The Radsone device delivers better notes energy and is much more transparent especially with treble region and the extension too feel much more resolving. It has a juicier and musical tonality compared to the more serious sounding HUD100 MK2.


Unlike the HUD100 the ES100 has a slight bit of bias towards the lower end and delivers voluminous, fuller and fun sounding notes. It delivers excellent sub-bass extension which is very deep and rumbly. The mid bass is slightly more emphasized but it barely has any impact on the earphones true character. The upper bass is detailed and is clear of any type of ambitious advances. When used with flat sounding earphones things get very interesting as it adds a bit more thump making things more enjoyable. When paired with bassy IEMs it does not push the notes off the limit, maintaining good amount control, better than Hip-DAC. The decay speed is nicely paced (Faster than Hip DAC and slightly slower than HUD100) giving it the required amount of precipitation and very good texture.


The ES100 MK2 stays true to Radsone’s reputation and delivers transparent and clear mid range. There is no emphasis of any type but the vocals do sound clean and natural. Notes have appropriate decay and agility. It has a very good balance of attack, aggressiveness and musicality.  Notes are fairly clear of any kind of sibilance or harshness with both vocals and upper treble region. Reasonably fast decay helps notes deliver good clarity to background instruments. Micro details are as good as similarly priced desktop DAC/Amps. Vocals have very good amount of texture and tonality along with very good details and clarity. Both male and female vocals are aptly accurate and precise. The upper mid region has no anomalies to worry about while delivering excellent clarity and details.


ES100 Mk2’s treble is on the more neutral side with a more musical yes accurate timber. It delivers without exaggerating the notes while maintaining good amount relevance and clarity. The presentation is neutral and doesn’t have any coloration and pairs excellently with wide variety of headphones and earphones without any problem.

The energy is slightly lacking and the presentation is not over energetic or tingly while the directional cues are a bit inferior to the HUD100 mk2. Notes have good sharpness and clarity. Details are very good. The treble extension is nothing to complain about and the bigger than average stage size gives it nice resolution and imaging.

SOUND (Wireless):-

There isn’t much separating the wireless and wired sound. The wireless mode favors a bit more of lower end body while delivering a bit slower decay. Mid range is very good but lacks a little bit of micro details. The treble is slightly less sparkly and the extension is not as good as the wired mode.


What is good DAC/Amp without proper staging and imaging? The ES100 mk2 delivers a very cohesive imaging with a nicely rounded stage. It has very good depth, height and width but the depth is slightly shorter than the height. Imaging is very good with good presence outside the head, the lower end along with the vocal region are placed inside the head while most of the instruments are placed outside the head giving a nice holographic projection. The 100 Mk2 delivers an evenly spread stage with good notes distribution. It doesn’t feel clumsy or congested. Layering is very good with nice background and foreground separation.


VS HUD100 Mk2:-

HUD100 mk2 is targeted towards a different type of consumers who has wired connectivity as priority and likes to use it with their PCs along with mobile phones. It houses a slightly better chip but lacks a lot of stuff like BT connectivity, balanced output and built-in battery.

When it comes to sound the ES100 mk2 is only 2nd to the dedicated USB-DAC of HUD100 mk2. HUD100 mk2 sounds cleaner, a bit more transparent with crispier and contrasty notes. The ES100 mk2 has slightly more bass volume while lacking a bit of treble spark and extension. There isn’t much separating the two as the in-house tonality and tuning principal is the same.

ES100 mk2 is a better all-rounder but the HUD100 mk2 has its priority set and excels at what it does.


The advantages are clear.

1. Its small enough.

2. Can be used as wired and wireless DAC/AMP.

3. Has enough power for most of the earphones and headphones.

4. The sound quality is very good irrespective of the mode of usage. It just resolves a lot more than its size suggests.

5. It can be clipped on clothes.

Negative points:-

1. The build quality can be better.

2. The micro USB port has to go.

If you are in the market looking of a Bluetooth DAC/Amp with occasional USB DAC usage with mobile phone or PCs, the Radsone EarStudio ES100 MK2 should be one of the best option, much more recommendable than the cheaper dongles and even the Hip DAC.


About Author

My humble audiophile journey started in 2010, when I was in college, where I fell in love with the elements, nuances, and variations of this mesmerizing world. The ability of tiny earphones to recreate amazing sounds made my bad days tolerable and good days better! Now I am a full-time audiophile with a preference for musical tracks, especially vocals and engaging ones. I must admit I am addicted, but not to drugs or alcohol, but to earphones. Come join me as I share my experiences, bad or good, and let’s have some fun!

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