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Earstudio ES100 MKII – Bluetooth Receiver Extends My EQ

Earstudio ES100 MKII – Bluetooth Receiver Extends My EQ

Eartstudio ES100 MKII is an older bluetooth receiver, but one that everyone loved, and is priced at 90 USD at the moment of writing this full written review. It will be compared to FiiO BTR5, FiiO BTR3K, and Qudelix 5K



Earstudio is a really nice company, with tons of mini-sized accessories and which offers great warranty for everything they sell. I personally liked some of their products, and also experienced some products that I was not so enthusiastic about. Even for the same product, the HUD100, I loved their MK2 variant, but felt that the MK1 was underwhelming, so they are full of surprises. 

It should be noted that I have absolutely no affiliation with Earstudio. I’d like to thank Earstudio for providing the sample for this review. This review reflects my personal experience with the Earstudio ES100 MKII. Every opinion expressed is mine and I stand by it. The purpose of this review is to help those interested in Earstudio ES100 MKii find their next music companion. 


Product Link

You can always grab an ES100 MK2 from www.amazon.com here: https://amzn.to/2UdRZ0l

If you’re in the UK, you can also grab an ES100 MK2 from www.amazon.co.uk here: https://amzn.to/2Udz19Q

And if you’re from Europe, you can grab an ES100 MK2 from www.amazon.de here: https://amzn.to/3x7WLe7


Build Quality/Aesthetics/Functionality

The unboxing was way too simple to add a part of review to that, as the ES100 MK2 comes with just a short microUSB cable. That is it, no case, no covers, no extras. For the 90 USD paid, it is ok though, and comparable to what Qudelix does with their 5K

Now, the shape and ergonomics of ES100 MK2 are perfect, as it is extremely light, small, and has two headphone outputs, one in 2.5mm balanced mode, and one in 3.5mm single ended size. It can work as a USB DAC too, just like BTR5, but the short cable and the fact that it uses a microUSB connection are discouraging when it comes to recommending the ES100 MK2 as a USB DAC. 

The back of the unit has a small shirt clip, which seems to be made of metal, and the unit has FWD/BCKWD, VOL+ / VOL-, and a PLAY/On/OFF button. There is a LED Ring at the front, which cannot be turned off, and a microphone on the side, which can and will pick up a lot of noise if you brush it against your clothes. 

The face of the unit would’ve been perfect for a display, but there is none, BUT there  is a smartphone app that’s really handy, with EQ options, also with a passthrough mode that allows for the microphone to record the ambient noise and mix it with the music. In a simple way, it works as a hearing aid if you want it to, amplifying the ambient noise quite a lot. 

The battery life is decent, and the performance is outstanding. I never lost connection even with a wall in between the phone and ES100MK2, but the battery life is a bit low when driving hard to drive headphones and if using an LDAC connection. I always used LDAC, and it is stable, which is really cool for a budget Bluetooth receiver. It can get into overdrive mode, which you can see in the app, and that sounds exactly like it, overdriven. It also has a mode for twice the current if you want to drive harder stuff, like HIFIMAN Sundara, and this option does not lead to overdrive. 

All in all, the ES100 MK2 is pretty versatile, fairly potent for driving headphones, and has a low noise floor, being perfect for IEMs too. 


Sound Quality

This is one of those reviews I am making rather quickly after receiving the product, as I have zero hopes of ES100MKii burning in or something, and it is safe to proceed with writing my honest impressions about it. The overall sonic presentation is slightly warm, somewhat smooth up top, wide but not very deep, fairly punchy and fairly dynamic. The sound is marginally better when using ES100 MK2 as a DAC/AMp via the cable, than when using it as a Bluetooth receiver, but it is not practical, and since it has a microUSB cable, using it as a USB DAC will be less lived than DAC/AMPs with a Type-C connector. 

The bass if ES100MK2 is fairly deep and full, with a bit of warmth applied to the midrange too. The bass is not necessarily basshead, but it has good substance, and especially if you have a brighter, or neutral IEM, it should give them a bit more soul and life. Especially with Headphones like HIFIMAN HE400SE (review to come soon), I had an excellent overall experience, with good overall depth, good impact, and excellent overall dynamics. 

The midrange of the ES100MKii is clean, clear and has a good amount of width. The depth is actually quite low, and layering is not the best, but detail is great for the price, and the midrange is slightly warm, with a good amount of thickness to combat thin sounding IEMs / Headphones. This is a good spot to mention the great driving power, which is really comparable with what HUD100 MK2 has. There are filters too, for those who want to fine tune the textures of the ES100MKii, but the effects of changing the filter are really low, and I wouldn’t rely on those to make major changes to the sound. I also noticed a good amount of punch and a colorful presentation with ES100 and Verum One. It has an ok protection against low-impedance charges and won’t run into overcurrent or burn up when paired with Verum One (this is the lowest impedance load I have on hand for such tests). 

The treble of ES100MKii is fairly clean, somewhat soft and somewhat smooth, but with enough presence and sparkle to combat the neutral and bright sounding IEMS, especially those from your typical Chifi company like KZ. All in all, the signature is colorful in the mids, relaxing, and punchy, a good combination to turn it up and have fun even in one of those days when you really don’t feel all that Doki Doki. 



There are quite a few bluetooth receivers available on the market now, including some crazy expensive ones, and some affordable ones, but the most prominent competitors for ES100MK2 are FiiO BTR5, FiiO BTR3K and Qudelix 5K.

In terms of pairings, you can literally drive pretty much anything below 500 USD with ES100MK2, and just like HUD100MK2, it is perfect for both IEMs and Headphones, but ES100MKii has a balanced output too, not just a single ended one. So even BQEYZ Spring 2, or NX Ears Baso, MAS X5i, FiiO FH5S, or headphones like Verum One and HarmonicDyne Zeus will be driveable from ES100mkii. 

Earstudio ES 100 MK II vs FiiO BTR 5 (90 USD vs 120 USD) – The most important comparison is the first one, because when considering ES100MKii, you probably want to stay away from what seems to be the technically better option. In general, BTR5 is built better, with a more ergonomic body, but a heavier build. I prefer BTR5’s Interface and overall usage, but when it comes to the sound and connection, ES100MK2’s plastic body is better for bluetooth, where glass and metal isolate more and BTR5 will have a more fragile signal. The sound is actually comparable, with ES100MKii being warmer, wider and more colorful in the midrange. BTR5 is deeper, has more layering, and is more neutral, with slightly more detail, but the improved dynamics on ES100mk2 makes me grab it more often if I’m using something that’s already a bit neutral or bright. 

Earstudio ES 100 MK II vs FiiO BTR 3K (90 USD vs 70 USD) – BTR3K has a nice overall ergonomic build, but honestly and realistically speaking, ES100MK2 is much better as a bluetooth receiver. The only place where BTR3K wins hands-down is in overall design and aesthetics, as ES100MK2 looks plasticy and crackles if you press on it with enough pressure. The connection stability is better on ES100 MKii, the sound is more natural, has more dynamics, more detail, better driving power, and is generally more natural and versatile. 

Earstudio ES 100 MK II vs Qudelix 5K (90 USD vs 80 USD) – It feels a bit like 5K from Qudelix was made as a child of ES100MK2, but made by a different designer. The two bluetooth receivers have a similar build, similar overall build quality, similar concept, but different design and aesthetics. The overall audio performance is comparable, but 5K is a bit more neutral, manages to squeeze a bit more detail from music, but has much less dynamic, less driving power, and less overall realism to it, where ES100Mk2 is more punchy and warmer in the bass and mids. 


Value and Conclusion

Biggest question today is whether you want to purchase an alternative to BTR5, and if you need a bluetooth receiver. Earstudio themselves also make the HUD100MK2 which is better if you just need a DAC/AMP, as it has a type-c connection, and is even smaller, and made of metal. ES100Mk2 is actually perfect for those who just want a nice bluetooth receiver, but don’t want to stress much with what to get, and who like the aesthetics / design. Regarding whether I would recommend BTR5 more, I really wouldn’t, both receivers have their own pros and cons, and I highly suggest reading my review on BTR5 to get a better idea of where it stands too. 

The package is really basic, and the build quality is a bit plasticky, but ES100MK2 has a really solid connection to my phone, and is Bluetooth 5.0 enabled, with Hi-Res BT enabled too. It is able to keep a strong LDAC connection without losing signal, and it has a set of functions that other receivers don’t have, like sound pass-through, 2X current mode, overdrive mode, and a really practical multi-band EQ with variable Q values. 

The sound is open, dynamic, punchy and vivid too, detailed enough for the price point, with excellent overall substance and impact. 

All in all, ES100Mk2 is perfect for its price, and if you’re looking for a high-quality Bluetooth receiver, I fully recommend considering ES100Mk2 for its sonic performance, reliable connection and light weight. 


Product Link

You can always grab an ES100 MK2 from www.amazon.com here: https://amzn.to/2UdRZ0l

If you’re in the UK, you can also grab an ES100 MK2 from www.amazon.co.uk here: https://amzn.to/2Udz19Q

And if you’re from Europe, you can grab an ES100 MK2 from www.amazon.de here: https://amzn.to/3x7WLe7


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Full Playlist used for this review

We listened to more songs than those named in this playlist, but those are excellent for identifying a sonic signature.  I recommend trying most of the songs from this playlist, especially if you’re searching for new music! The playlists are different for Spotify, Tidal and Youtube, and based on the songs I enjoy and are available on each!




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  1. Jack Daniels

    > It feels a bit like 5K from Qudelix was made as a child of ES100MK2, but made by a different designer.

    Which is exactly the case because Woo-Suk Lee is CEO of Quadelix and former CTO of company that created ES100MK. Funny enough but Quadelix 5K also has issue with usb socket as its predecessor.


    1. Gheorghe Dobrescu

      Woah, that is good to know! I actually learned about this after I published the review, but left it in as an Easter Egg

  2. […] It will be compared to other DAC/AMPs and Bluetooth Receivers, including FiiO BTR5 (110 USD), Earstudio ES100 MKII (90 USD), Questyle M15 (250 USD), and iFi hip-dac2 (190 […]

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