RADSONE EARSTUDIO ES100: Bluetooth signal never sound so good

RADSONE ES100 (post-hype?) review:

VALUE: 9/10


How come one of the more sceptical dude about bluetooth technology sound quality became so interested in a Bluetooth device? How is it possible that even if he still don’t get intrigued by must BT iem or headphones and don’t care to try them, Nymphono was ready to sell an arm (but not its soul) for having the chance to write a review of this Earstudio first creation? Well, for two reason really, one being the hype that never go out of breath and second being the fact sound is processed trough a dual AKM dac before it feed your headphones or iem. Perhaps a third one would be: its not BT earphones and you can use all your favorite one with the ES100. Fourth could be as well that its LG G6 phone sound like soul less crap. ETC!


SO it make lot of reason why I decide to give a try to this wonderfull all-in-one bluetooth receiver. Its hard to understand how such a small portable device can hide that much features as well as having 3.5mm unbalanced and 2.5mm balanced phone out, a mic, usb-otg dac-amp fonction and BT decoding trough 2xAK4375a hifi dac. But thats not all, Earstudio have its own APP to control every features of its device, and this too suprise me alot, its not a basic app that just control volume, in fact it take the ES100 to a next audiophile level by letting him configure every aspect of dac potential. We will talk about this later.

Now lets just begin the review.


SPECS and some features:

Bluetooth DAC/Headphone Amp

LDAC, aptX-HD, AAC, aptX, SBC

14 Hours Playback

USB DAC/Headphone Amp

USB Audio Class 1.0 (48KHz / 16-bit only)

Works as Preamplifier in vehicles

3.5mm output to car AUX

CAR MODE support(auto power on/off)

Proprietary DualDrive Technology

  • Two AK4375a DAC/HPAMP ICs
  • 3.5mm Unbalanced output
  • 2.5mm Balanced output

Proprietary DCT algorithm (on/off option)

  • Eliminate noises in digital sound sources
  • Enhances 16bit into high resolution 24bit

Built-in Analog Volume control

Noise free even with high-sensitivity earphones

Hands-free call with built-in high sensitive microphone

Analog Output Upgrade Technology

Optimized circuit architecture using 2 independent Hi-Fi DACs and Amplifiers

2 selectable operating modes support 2x current or 2x voltage

Capable of driving headphones with high or low impedances

Delivering pure signal without any loss or distortion, and with enough power

AK4375a INFO:
The advanced audio devices have been specifically optimized for portable applications based on AKM’s VELVET SOUND architecture which is established by premium audio devices, realizing high quality sounds for music playback. As an audio device for mobile applications, the AK4375A achieves industry leading level performance of THD+N (-99dB) and 110dB dynamic range with newly developed 32-bit advanced audio DAC and cap-less class G headphone amplifier.
In addition, the AK4375A integrates asynchronous SRCs and crystal oscillator for jitter isolation to prevent degradations of analog characteristics and sound qualities by external clock jitter. It is suitable for audio devices with Hi-Fi function such as smartphones, tablets, portable music players and wireless headphones. The AK4375A is housed in an ultra-small space saving 36-pin CSP package.

Key Features
-1. Stereo High Sound Quality Low Power Advanced 32-bit DAC

– 4 types of Digital Filter for Sound Color Selection

-2. Ground-referenced Class-G Stereo Headphone-Amp

– Output Power: 25mW @ 32Ω, 40mW @ 16Ω, THD+N = 0.1%

– S/(N+D): 99dB

– S/N: 110dB

– Output Noise Level: -119dBV (Analog Volume ≤ -14dB)




This device is not about the look at all, it have a low profile approach in a very small body. Its all plastic with the exception of metal clip. I would have love at least to have metal headphone output of better quality, but it do not change anything for the sound, perhaps the durability tough. So yeah, perhaps too much plastic.

P2160637.JPG P2160638.JPG P2160639.JPG P2160647.JPG

For the design, its simple and quite intuitive to use, but buttons are very small and there not lot of pression space to feel the click, I would have prefer separate buttons for volume up and down and changing tracks, so it could help to blindly use them. As well, there a light that tell you when device is connected as usb dac (flashing green-red), BT dac (flashing green) or when you shut it down (red) ,the light is not extremely visible wich is perhaps due to plastic being not enough transparent. It’s very subjective whim about how to make ES100 design interface perfect, so its to take with a grain of salt.

Interface is still quite simple, as said, there volume control at one side and tracks control at the other side with starting-shutting button above it. It easily connect to any device and will even connect freely when you open BT of your phone if ES100 is powered on, no need to always struggle with setting, wich is a joy to use.

BATTERY life is very good, going from 8 to 14 hours depending of volume or output you choose, 2.5mm is less power hungry than 3.5 for example.

BT signal distance is about standard but in a very trustable way, in a distance of 12 meter I do not have any connection problem. If I hide myself behind a wall of brick it can interfer with signal…as every BT iem or receiver.

USB DAC work perfectly, its plug and play like everything with ES100, you just never need to struggle about anything. The sound is identical to BT version, but perhaps have a blackest background.



Companion Android / iOS Application

  • Codec selection
  • 2.5mm / 3.5mm output mode selection
  • Battery level status
  • Analog & Digital volume control
  • 10-Band Embedded GEQ control
  • AK4375a DAC filter selection/ Oversampling selection
  • Proprietary DCT level control
  • Cross-feed level control
  • Microphone gain control
  • Ambient mode On/Off

The Earstudio application is a MUST, you can use the device without it and it will be recognize easily by your sound source like a non adroid based DAP with BT, but for a phone it take the ES100 to next level. With this app you can control whole potential of dual dac chips, you can choose type of current output like normal or high performance for 3.5mm so it will give about 1 or 2 times current power, you can use a top of the line EQ that work wonderfully, you can change source and analogue volume, buffer lenght, multipoint pairing, over sampling rate, crossfeed, mic volume and even ambient mode that make you ear outside noise so you can stay alert in urban survival mode. Man, there too much features to explain so its really up to you to discover them and earstudio understand this by explaining every aspect of there features.

Anyway, I will talk about features that I feel can improve sound rendering like.

3.5mm HIGH PERFORMANCE MODE vs 2.5mm Balanced Mode:

For me, the unbalanced way is in High performance mode 99% of the time even with must of my IEM because I feel it give better dynamic and imaging than normal mode.
The opposite happen for balanced mode, I use normal 99% of the time as it give plenty of power and an overall better sound than unbalanced mode, in a very subtle way that will be more hearable at high volume. Wich is overall better clarity and layering with near perfect black background. Don’t use High voltage mode with iem, its just too powerfull really, but for high impendance earbuds like the HE150ohm it is quite appreciate.



I sometime play with this and confirm it give very subtle sound difference for the dac Filter, more about attack decay, but its more hearable in balanced mode. For the Oversampling, its very strange but can improve details and texture of lossy files like MP3, anyway, I feel it can stole some air between instruments too. Both are for maniac audiophile really.


Capture+_2019-02-15-13-59-41.png Capture+_2019-02-16-16-46-04.png

I’m not a big EQ user, because must included with DAP did not work well, but this one take me by suprise and is fun to play with as well. It really can modulate sound rendering precisely and I solve some earbuds and iem sound issue with it, like earbuds that was bass anemic became more bassy without creating distortion or artificial rendering, wich was just incredible really. This EQ is a masterpiece IMO.



Theorically bluetooth signal should sound inferior to direct connection to audio source, but in this case, as it use different high quality dac processing and amp module than stock one on your phone its really a game changer for must of phone but perhaps exceptional one with quad sabre dac like V20 or V30, but even them will not have as much amping power due to powerfull balanced output power of ES100. As well L-DAC is lossless processing for must 48khz 16bit flac music and lower rate one, so, this is litterally an audio revolution.

Balanced Output give the better sound performance by slightly improving resolution and overall clarity due to lower THD and blacker noise floor, but 90% of the time I use unbalanced output for simplicity and versatility as well as because I do not need high amping power form my iem, so impressions are with unbalanced output using 48khz flac and 320kbps mp3.

I will describe overall sound processing of dual AK Dac as extremely well layered, smoothly detailed and wide sounding with lot of extra deepnest to it. It have the capacity of extraction more sound info and give extra excitment to the music you think you know, like if a veil was pulled off wich permit you to perceive whole audio range of your favorite music without it feel artificial or too analytical. As well, I feel it give extra energy and dynamic to the sound, especially mid bass that feel more controled and way less boomy than lot of phone audio, like my G6 or even more my Ipod touch. In some way, if you do not listen to wide music style, perhaps the audio revolution you get will be minimal, but with great quality recording it is an evidence that this bluetooth receiver can transform your music into audiophile experience mustly seen in good quality DAP.

As said, with balanced output it take audio quality to an even more pristine level of clarity and dynamic, so if you have iem with detachable cable, order some 10-30$ balanced cable from Aliexpress ASAP! You will be utterly happy of little extra investment.




The X3II have a dac chip from same Asahi Kasei microdevice japanese maker, but this time its a single premium AK4490, wich can achieve higher resolution specs, but as the ES100 use dual AK4375a with dual amps the game here is change. Anyway, I will just talk about overall soundsignature difference of both device, using same music tracks including 320kbps mp3, but mustly 48 or 96khz flac file. ES100 will be drive trough Bluetooth Ldac from my LG G6 and X3ii directly from audio output at high gain.

What hit me first by comparing these two is how overly smooth sounding is X3ii compared to the more energic ES100, should it be with Monk+, Tinaudio T2 or Takstar PRO82 headphones, the ES100 sound more lively and fowards, wich give more sens of deepness and tigher bass presence. The X3II in other hands have slightly more finess and transparency, but in a wide panoramic approach while the ES100 have space between instrument layering instead of transparent veil.

BASS of X3II feel less impactfull and full bodied, especially in mid bass where the punch is smoothed while the ES100 is a little emphased and have tigh fast approach that never feel hollow even if not with as much decay than X3II.

MIDS are similar here, but again, vocal feel more separate and fowards with the ES100 even if X3II have some extra presence emphasis in this region. ES100 is more detailed and have overall better resolved mids because of extra precise layering.

TREBLE extension of both is good, but because of a smoothed out soundsignature, X3ii feel less detailed even if more sparkly when micro details appear. ES100 have great clairty but do not have long decay in highs presentation, wich permit to have less mixed up soundstage when fast complext tracks with lot of instrument have to be dealt with.

About amping, even if X3II is suppose to be slightly more powerfull, I tend to push volume higher with it to have more sound pressure and compensate its lack of energy and impact.

VS XDUOO X3 (110$) :

The X3 have a more fowards energic sound presentation with an overall better resolution but to the cost of being sometime overly agressive. Bass is thigher and some time too textured and lacking extend after attack where the ES100 is smoother but still fast with more transparent and vast presentation. Mids of ES100 sound wider too, with a hint more smooth natural presence while X3 have greater textured mids with better separation but a lack of fullness in body. Treble extension of both is very good, but I feel the X3 have more focus on it with a blackest background noise floor, but strangely, its the ES100 that have more decay after note impact. In conclusion, I would say ES100 is better suited for bright or sharp iem headphone as it will never create hissing or sibilance while X3 will be more benefic for warm or smooth iem even if he can have great sinergy with near everithing.

VS LG G6 smarthphone :

Firstly, ES100 is way more powerfull and can drive at higher volume whatever you use 3.5mm or 2.5mm balanced output. Amping difference with balanced is extreme. About the sound, G6 feel like an absurd lifeless sounding toy with overcompressed, constraint soundstage, bad layering and imaging, lack of dynamic and details, so when you plug in ES100 to continue same tracks that was playing on stock G6 difference is night and day and you find yourself freely listening to real musicality in a enormous soundstage with great deepness and a lively layering that make sound frequencies fly around you and understand why you need a Radstone ES100 to finally listen to music with your weak anemic sounding smarthphone. The step is so big that I can’t imagine anybody not hearing positive difference unlike when comparaing to good quality DAP wich feel more subtle. It was easy to compare both device using ES100 BT connection as I can listen the same track on G6 without having to change any setup, and yeah, I close my eyes to do ‘’blind testing’’ hehe

Headphones, iem, earbuds Sinergy:


With MONK+:

To me the Monk+ need quite good and clear amping to shine at full potential, and i’ve been surprise to see the ES100 can drive them perfectly. The monk sound very energic and well layered with the ES100, and it tend to make them even more neutral as the mids feel less fowards. Level of resolution is excellent as well as near supreme black background floor. Perhaps I would love a little more mids colouration this time tough, depending of music style.

With Takstar PRO82:

This is a magnificent sinergy that solve every problem with PRO82 and make it sound more balanced and energic solving its brightness issue that can occur with Xduoo X3 (first gen) and Xduoo X20. Bass became more tigh and well separated, gaining a rounder body too, mids are clearer and less recessed. All in all, we gain a better imaging and layering and loose some highs harsness too.

With Meze 99 Neo:

At 26ohm, the Neo are very easy to drive so ES100 have no problem making them shine. I feel the bass was more tigh even if punch gain in authority, the spacious soundstage was perfectly layered without any harshness, it was a warm but more energic presentation that give Meze extra life and faster presentation than with smoother DAP like X3II. Very engaging sound experience and now i’m curious to know how it could sound with balanced output….need to find a cable ASAP!

With TinAudio T2:

Here, the T2 gain a little much needed mid bass punch as well as hint more rolled off sub without loosing any of its great layering. Soundstage became a little less airy but not in a bad sens as it give more energic agile sound and that with a good clarity and quite black noise floor even if T2 sound more smooth than with ultra clear source like Xduoo X20. For a BT decoding music performance, its outstanding. To note : Using the T2 with 2.5mm balanced output clearly improve clarity and dynamic as well as giving a blacker background, this take me by surprise and i will not go back to unbalanced cable for this iem.



The Radstone ES100 is a phenomenal bluetooth receiver with excellent sound quality, good 3.5 ouput power and powerfull 2.5 balanced output. It have all the features any audiophile could dream of and its battery life is excellent. This take bluetooth sound to the next level with its great dual AK4375a DAC, its DCT technology that transform 16bit into 24bit and L-DAC, Aptx-HD (etc) codec compatibility. Earstudio put lot of work into creating this audio device wich is even more impressive to use with the dedicate application to control it. I really think this is a must have to any phone user that either want better sound quality, more amping for demanding headphones or extra portability that will not drain the phone battery life.
Earstudio is a new comer in audio world and deserve alot of respect, one thing sure, I will follow the evolution of this extremely promising company in the futur. Now that I know bluetooth technology can sound this good, I became interested in something I always been sceptical about and humbly admit BT codec transmission will must certainly achieve high end sound transmission in a very near futur. The hype is far from being finish with the Radsone ES100, and it will surely still be used in years to come.
BIG Applause for Earstudio audio team!!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s