Radsone EarStudio ES100: Deserving of the Hype


Today we’re checking out the ES100, a Bluetooth receiver from Radsone.

Radsone is a consumer electronics and technology company based out of Seoul, Korea, founded in 2011. Their technology (https://www.radsone.com/technology) is used by some heavy hitters in the industry, like Audio Technica, LG, and Qualcomm, so you know they’ve got some serious talent under their belt.

We’re not here to talk about that though. No, we’re here because of the ES100. This little Bluetooth receiver has been lighting up the online forums this past year. This device has garnered a lot of attention from the audio community for it’s impressive combination of tech and features offered at a more than reasonable price.

Let’s take a closer look.




I reached out to Radsone to see if they’d be willing to send over a sample of the ES100 for the purposes of review. They said yes, as evidenced by the review you’re reading. The thoughts and impressions within this review and my own based on my experiences with the ES100. They do not represent Radsone or any other entity. Should wish to pick one up, and you should if you enjoy Bluetooth devices, you can check it out here; https://www.radsone.com/earstudio. Make sure you scroll to the bottom of the page to ensure you’re ordering through an authorized retailer.

If you want a more technical look at this device, I HIGHLY recommend checking out this stellar review from yuriv on Head-fi: https://www.head-fi.org/showcase/radsone-earstudio-es100.23284/reviews

Tested with device firmware version 1.4.2.

Package Contents:

Disregard the condition of the packaging in my pictures. Seems Canada Post had it’s way with the ES100 during shipping…

  • ES100 Bluetooth Receiver
  • Micro USB cable
  • Quick start manual


Output RMS Power

– 3.5mm Unbalanced: 1.1 V

– 2.5mm Balanced: 2.2 V

SNR* (1KHz, 20KHz AES17)

– 3.5mm Unbalanced: 109dB (+2.8dBu)

2.5mm Balanced: 110dB (+8.8dBu)

Output Impedance

– 0.5~1 ohm

Bluetooth Range

– 10 meters

THD+N* (1KHz, 20KHz AES17)

– 3.5mm Unbalanced: 0.0022%

– 2.5mm Balanced: 0.0014%


– LDAC, aptX-HD, AAC, aptX, SBC


– 14 hours





Build and Ergonomics:

The ES100 is mostly plastic with a very simple, clean design and a professional silver on grey color scheme. Metal is used for the clip on the back, helping out with durability in the long run. The clip’s clamping force was fine in my opinion, but I’ve seen others finding it a little on the weak side. Not an issue I had, but worth noting anyway. Seams between the component parts are quite visible but line up properly without any sloppy gaps, including around the micro-USB, 2.5mm balanced output, and 3.5mm unbalanced output. To the right of the volume rocker on one side is a small grill behind which is the microphone for phone calls and the ambient sound feature. To the left is the 3.5mm output. On the other side of the unit is a rocker button for skipping through tracks, a pause/play button, and the 2.5mm balanced output. The face of the unit looks like a plain grey slab, though when in use you find there is an LED ring hidden beneath. The LED ring performs a number of functions, besides telling you if the device is on or not, using green, red, or blue colorings. I didn’t bother to memorize the various notifications, simply because it wasn’t necessary. The ES100 is easy to use and works exactly as you would expect.

The buttons used to interact with the ES100 are small and nondescript with limited physical feedback when pressed. I personally found myself routinely pressing the wrong thing, resorting to looking at the device most of the time to adjust volume, or swap tracks. This was even after a month of routine use, though I’ve gotten used to it by now. If Radsone ever decides to revise the ES100, I would love to see them change up the buttons so that they are easier to tell apart without looking, and provide a more prominent click when pressed. It’s a simple quality of life thing. The device is fine to interact with as is, but it could be better with some minor revisions.


The ES100’s Bluetooth performance is quite positive. Starting with connection strength, in regular use I didn’t have to worry about device placement. It could be in a pocket, clipped to my sleeve or shirt collar, or in my hand and dropouts weren’t a worry. It has a 30 foot range which is about standard, and like most devices with that rating can really only achieve it when unobstructed. I liked to use it when connected to my computer or LG G6. Those devices could be left on the living room table, and I would be free to walk nearly anywhere in the apartment without experiencing dropouts. Heading to my office or the front door would put two walls between myself and the device which would lead to stuttering, but the connection would hold. Overall connection strength is quite good.

The ES100 can connect two two devices at a time. It works fine and has remained tied to my LG G6 and Asus FX53V without the need to re-pair throughout the duration of my testing. I’m not sure what Bluetooth codecs my laptop supports, but they’re not fantastic as evidenced by the audio delay while watching videos. Connected to my LG G6 over aptX HD or LDAC (defaults to LDAC) there is no delay that I could notice, making for pleasant video experiences.

Sound Quality:

Sound quality, regardless of whether you’re using the ES100 over Bluetooth or USB (16bit max via USB on anything but macOS), balanced or unbalanced, is excellent. The two AK4375a DAC/AMP chips from Asahi Kasei provide plenty of driving power along with a warm leaning and smooth but very resolving signature. Some might describe it as an analogue sound. Unlike other products with similar traits, I didn’t find the ES100 restricted to earphones with certain signatures. Whether it was being paired with the neutral and very detailed Astrotec Delphinus 5 or smooth and bassy Meze 99 Neo, pairings always sounded great. It’s a very versatile product, a quality aided greatly by it’s low output impedance.

The ES100 has almost completely replaced my other portable headphone amps (Walnut F1 and Auglamour GR-1). Not only does it sound better regardless of how you’re opting to connect to your device, but its also smaller, lighter, and has a vastly longer battery life.



Companion App:

The Earstudio app for Android or iOS gives the ES100 a TON of extra versatility and is an absolute must if you want to get the most out of it.

From the home screen you have a number of options. Swipe right and a menu pops out from the left containing a slew of options, like searching for a device to connect to, LED functions, the manual, factory reset, and much more. Closing that menu, from the main screen you can also select input to change the codec, buffer length, hands-free profiles, output via USB DAC, mess around with Radsone’s HD Jitter Cleaner, and even check out measurement graphs showing off the ES100’s single tone performance with a variety of cell phones. Under output you can optimize the quality of the sound being pushed out through the 3.5mm and 2.5mm TRRS ports. Under 3.5mm you can select either Normal or High Performance modes. The high perfomance mode reduces the output impedance by nearly half (~1ohm to ~0.5ohm) resulting in a cleaner sound. Under 2.5mm you can select from Normal or High Voltage modes. The High Voltage mode doesn’t change performance and simply doubles the voltage from 3.2v peak-to-peak to 6.4v peak-to-peak allowing you to drive some pretty demanding gear. They even provide an explanation of why balanced is superior, namely it reduces noise ground noise providing a cleaner sound. Going back to the home screen, you can also adjust the analog volume and source volume. Under analog volume you can adjust each channel separately by up to 6dB, set the max volume limit, and even estimate how loud you are listening when using the ES100 as a headphone amp by entering the impedance and sensitivity of your headphones. Cool!

Next up is the equalizer. You’re provided a preamp which can be adjusted +12dB or -12dB. Then you have ten sliders for adjusting a variety of frequencies; 31.5, 63, 125, 500, 1k, 2k, 4k, 8k, and 16k. Below that you have 12 distinct preset EQ options like Classical, Jazz, and Bass Reducer, as well as four presets that you can save specific EQ settings too. They can be renamed as well, so you never have to guess which is being used to tame the aggressive treble peak on your HiFiMan RE800.

Next up under Sound Control, you can adjust how aggressively the app will compensate for and remove digital noise via the DCT level. Crossfeed can also be adjusted. Note that these options will be disables if connected via LDAC as they are not supported. Further down you can apply one of four digital filters to the AK4375a DAC, and if you need, play around with the over sampling rate.

Last up is the Ambient Sound feature. This is something I was surprised to see included and not mentioned anywhere on Radsone’s site. Most companies brag about such a feature whenever possible. Turning Ambient Sound on uses the ES100’s in-built mic to pic up and feed in outside noise so that you can still hear your surroundings. When using this feature outdoors, unless the earphones or headphones I was using were unusually naturally well-isolating, aided further with foam tips, Ambient Sound wasn’t as helpful as I was hoping. If the mic sensitivity was left fairly low, it didn’t pick up important noises. Increasing the mic’s sensitivity enough so that it would pic up sounds a decent distance away also resulted in every little brush and scrape against my clothes to be picked up leading to a very noisy and unpleasant experience. I found it most useful indoors where I could set the ES100 down beside me in a stationary position.

As mentioned before, the app is filled to the brim with features and functionality and it really lets you tailor the ES100 to suit you and your listening behaviours and preferences. I imagine they put a ton of time into it, and it absolutely paid off. Best of all, if you’re like me and are still learning the ins and outs of audio terminology and what does what, just click the numerous question marks to the right of most features for well written descriptions of what they do, why they’re important, and how to use them. Odd as it is, it one of my favorite parts of the app.



Final Thoughts:

If you’re a fan of high quality, portable audio and have been holding off on getting into wireless due to questionable audio quality, you’re safe to dive in with the ES100. If you enjoy cool tech and love messing around with apps and features and fine tuning your audio experience, this is a great product for you. You can tweak until your heart is content. If you are the exact opposite and want something simple and easy to use, forgo the app and run the ES100 as a bare bones Bluetooth receiver. You’ll still have an awesome time. This is great product for pretty much anyone. If I were to complain about anything, it would be the tiny, nondescript buttons that can be difficult to tell apart, something that will no longer be an issue once you have used to device for a while.

At only 99.00 USD, the ES100 is beyond being an easy recommendation to any fan of portable audio. I don’t say this often, but it lives up to the hype. Great job Radsone. Seriously.

Thanks for reading!

– B9Scrambler

2 thoughts on “Radsone EarStudio ES100: Deserving of the Hype

  1. Hey again,

    Did you test this during any sort of exercise? I am still debating on getting the ES100 or a bluetooth cable of some sort but I am heavily leaning towards the ES100. I have read the clip isn’t that great and I am just trying to picture what I may do with this during running, lifting, etc. Thinking about spending up a bit and pairing the ES100 with some iBasso IT01s.

    Thanks so much!


    1. Hi Matt. Not really, just walks and some biking. The clip is durable enough in my opinion, but doesn’t clamp with a ton of force. I suspect it will be fine for the majority of activities, as long as it’s not too vigorous. I found it light enough to clip onto my shirt collar and other areas without it feeling intrusive, though most of the time I just chuck it into the breast pocket of my sweater, or clip it to the pocket of my jeans.


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