EarMen ST-Amp

EarMen ST-AMP​

EarMen ST-AMP
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Prelude:
There are companies that simply do not need to be introduced, one of such companies, despite their still young age in the pages of history, is EarMen, proving at every step that a small sea can be beautiful. By constantly breaking the barrier of technological limitations, it proves how important it is to approach each component in order to create and achieve success. Today we will take a look at their next creation, EarMen ST-AMP. Initially priced at USD 599, it is now available at an excellent and very competitive price.



Unboxing and execution:
The rigid cardboard packaging contains the device itself, which is a medium-sized body, and a short operating manual. It’s a pity that there is no power cord, but on the other hand it allows us to reduce the amount of electronic waste. The device itself is elegant and aesthetic, and the quality of workmanship is at the highest level. On the back there is a USB B input, unfortunately also without the appropriate cable in the set, a 4.4mm balanced input and output, an RCA input and a pre RCA output. On the front panel there is a button to turn on the device, a digital-analog switch, a large jack output and a balanced 4.4 mm output, as well as a solid-looking potentiometer operating in the analog domain. Actually, that’s it for technical issues. It is worth noting that the size of the ST-AMP is perfect for placing, for example, a TRADUTTO DAC on it.


Sound:
DAC Mode:
The DAC implemented in ST-AMP is a well-known solution from ESS, but its selection is not accidental, and the timbre and signature perfectly complement the overall tuning. In this mode, if we use the built-in transducer, we get a complete and entertaining sound, perfect for quiet listening. The amount of information is huge, the detail and dynamics are at the highest level. And the pre output ensures great results.

Bass: The bass itself is fast and dynamic, and its resolving and entertaining character, close to realism and natural-neutral timbre, perfectly reflects the idea of tuning the EarMen. There is a lot of bass, and the base of the lower bands is clearly noticeable. It is an entertaining and engaging musical message that allows us to engage with the music effortlessly. Not for a moment did I feel overwhelmed or overexposed to low frequencies, which I highly praise EarMen for.

Midrange: Extremely clean, close to neutral. Where I could really feel the advantages and craftsmanship of ST-AMP tuning were the vocal sections, where the realism of the sound exceeded my wildest expectations. The amount of detail and information turned out to be more than enough to enjoy beautiful and emotional music. It’s amazing how dynamic and encouraging music can be. The sound stage generated by the st-amp is really large with great width and pleasant depth, which allows me to become an element of my music and its integral part. High neutrality will also allow us to enjoy our music as it really is.

Treble:The highs were smooth and consistent, and the resolution exceeded my expectations for this price point. In the higher tones, in addition to great resolution and neutral transparency, I noticed a lot of air without unnecessary coloration or artificially increasing resolution at the expense of sound. I really like this approach to tuning and it’s something every manufacturer should strive for. Pop and jazz songs sounded extremely engaging, and the separation and resolution of the instruments were exemplary.


AMP Mode:
First of all, let’s start with the fact that ST-AMP only seems to be a simple device, because despite the lack of gain control and a large amount of power in the balanced mode, it is able to detect which socket is currently loaded. We will certainly not run out of power, although the SE output has much less power, which allows us to easily use IEM headphones for which excess power is not always desirable. Let’s move on
EarMen ST-AMP paired with EarMen Tradutto DAC.
As for Tradutto, you can read my full review in the next article. This is one of the best DACs up to PLN 1,000 and one of the best implementations of the SABER converter on the market, in my opinion. ST-AMP itself is quite neutral and perfectly reflects the character of the DAC itself. The sound has become much more resolved, deeper and more musical. Of course, I like the stock ST-AMP configuration, but Tradutto took the sound a few classes higher. The resolution has become noticeably better. I think these devices work great together.
ST-AMP paired with EarMen angel DAC.
In this combination, the sound became even more linear and smooth, the neutrality of Angel translated into an even more analytical and resolving presentation. Tradutto resulted in a more musical and dense sound, while Angel resulted in an even more neutral and technical side of the sound.


Comparisons:

EarMen ST-AMP (599USD/200USD) VS xDuoo TA01B (150USD)
I took the liberty of comparing these two amplifiers because the current price of the ST-AMP is close to my favorite DAC/AMP with a tube, which is the old and no longer produced model from xDuoo TA-01B. xDuoo is a darker, more compressed, but also definitely warmer amplifier, so overall, in terms of technology and resolution, the ST-AMP is definitely the winner, but the TA01B defends itself with a tube color, which I personally like very much, but it is not so universal and versatile. like tuning ST-AMP especially when paired with Tradutto.

EarMen ST-AMP (599USD/200USD) VS HIFIMAN EF600 (799USD)
Overall, the EF600 has much more power, which is its huge advantage, but at the same time it makes it unsuitable for in-ear models, in this respect ST-AMP is much more affordable. When it comes to the DAC section, the R2R in the EF600 is definitely something amazing. However, ST-AMP has better technical sound parameters, so it all comes down to individual preferences. Personally, I cannot imagine music without both devices, which are completely different from each other and at the same time complement each other perfectly. That’s why I can’t pick a leader and I recommend both devices as something really worth attention.



Summary:
EarMen has once again proven its position in the audio scene. ST-AMP at the original price of USD 599 was an extremely interesting proposition, and at the current price it is simply the undisputed number one. It is a great and complete device both as a stand-alone DAC/AMP, as a DAC with a pre function, or finally in my favorite role, i.e. a stand-alone amplifier. The headphone outputs are so well thought out that we can use virtually any type of headphones. The amount of power is more than enough for most headphones. The sound itself is close to neutral, but a realistic and engaging presentation has not been forgotten. This is undoubtedly one of those amplifiers that charms you and makes you addicted to it, just like the EF600. That’s why I highly recommend auditioning. The only thing I would change is to add a few percent to the price and make sure that the buyer does not have to worry about additional accessories. It would be good to see a power cord and at least a basic 4.4-4.4 AUX in the box. However, the sound and functionality completely compensate for this minimal drawback. My final assessment of ST-AMP is as follows: it is one of my favorite amplifiers, so I really recommend it. When it comes to the DAC section, it is well implemented, but it sounded best to me as a trsdutto DAC.

General/Packaging/Build
For those who are not familiar with Earmen, Earmen is a company registered in the US, and a subsidiary of Auris Audio which is a high end Serbian brand that builds amplifiers as well as headphone amps, similar to Auris Audio, although Earmen is registered in the US, all of the products are made in Europe to uphold a certain quality standard.

I have the ST-Amp with me today, a fully balanced amplifier, although it has a DAC (ES9280) in it, its strength lies on the amping section rather than the DAC, while it is certainly good to have for those who are on a budget or looking to get an external DAC to fully utilise the amp of ST-Amp.

Build quality of the ST-Amp is solid, switches are not wobbly, the input and output ports are gold plated and have solid connection (doesn’t come off easily). The only complaint that I have is with the positioning of the anti-slip rubber pad which formed a triangle, which in my opinion isn't that stable as it can easily topple if you accidentally knock it or if you have a thick power cord, it may be an issue as well. The amp itself has a noiseless LPS (Linear Power Supply) built in, which is something that i personally preferred instead of having a separate power brick dangling around

The ST-Amp came in a bare minimal packaging but is well protected, one box contained the ST-Amp, while another layer of box served as a protection layer. It doesn’t come with any power chord nor usb cable unfortunately, but for someone who’s already spending this much amount of money, they should already have several power cord or usb cables laying around, but nonetheless, it’s good to have so a first timer can enjoy the package right out the box.



Technical Specifications grabbed from ST-Amp’s product page
Full product information


IEMs/Headphones/Equipments used for this review

• Final Audio Heaven II 3.5mm
• Kiwi Ears Orchestra Lite 3.5mm
• Kiwi Ears Quartet 3.5mm
• Hidizs MS5 4.4mm
• Earmen Angel -> Earmen ST-Amp
• Xduoo XA-10 -> Earmen ST-Amp
• Sony WM1A -> Earmen ST-Amp

*Earmen ST-Amp is sent over by Miroslav from Earmen for the purpose of this review. I appreciate the opportunity given



Foreword
My review is solely based on what I hear via my equipment and I never consider my reviews to be objective in any way rather a subjective approach. Do take into consideration that everyone’s ear anatomy is not the same, so the psychoacoustics perception might be different as well, but i believe it will not stray too far. I have used the Angel for several months prior to writing this review.

Notable Features

• No loud popping sound upon switching the amp on or off
• Clean and dark background, no audible noise floor even on Hidizs MS5, which has quite low impedance at 5.3ohm, no noise/hiss at all
• Very very little channel imbalance at low volume, pretty much can be ignored even for IEM users, 3rd lining onwards there will be no imbalance anymore, unlike the implementation on some other dac amp, where it is either too soft or too loud, this is not the case here with the ST-Amp

Sound Impression
Listening to both the SE and BAL out, it’s safe to say that the SE doesn’t sound bad compared to the BAL out,, except slightly lacking in terms of dynamics, which is expected from SE output, i have tested some dac/amp which i shall not name to remain neutral, the SE output sounded bad compared to the BAL out, it is as if the SE’s circuit is designed badly and the focus is only on the BAL out. This is not the case for ST-Amp, both are sharing the same topology with almost no additional noise or THD as stated from Earmen, which I can personally attest to.

DAC Amp Combo

• Utilising the internal dac of ST-Amp, which is the ES9280, the DAC exhibited clean lows with good enough texture, sufficient punch and good resolution and dynamics, tonality wise, it is on the slight cool side and it has very good synergy with my transducers that has warm signature, for those with neutral signature, the sound is very dynamic and enjoyable when you feel the need to tap your foot

Amp + Xduoo XA-10

• Operating as Amp only, the ST-Amp is very revealing, uncolored, as well as dynamic. It bring out the characteristics of the DAC connected to it, take Xduoo’s XA-10 for example, which has dual AK4493 DAC, on its own, it doesn’t sound engaging, lows lacks a little texture as well as punch, resolution sounds a little lacking as well, when paired with the ST-Amp, the difference is day and night and i’m not kidding, very clean presentation overall while retaining the AKM’s “flavour”, resolution is also much better, the performance of this amp is simply excellent!
• Bass has better texture and slightly more weight to it, treble has good energy to it while maintaining its smoothness and dynamic

Amp + Earmen Angel

• Earmen Angel itself is an excellent device which i have also reviewed previously, it exhibits very clean and good dynamics
• Paired with ST-Amp, the dynamics of Angel is another step up from its internal amp, it sounds more dynamic, also a little more analytical, and transparent compared to its internal amp
• The reason i said what i said above is because i used the Final Audio’s Heaven II, which is a single BA IEM, listened via ST-Amp’s dac and amp combo, bass is slightly lacking and doesn’t have good texture/definition, switching over to Angel, i can immediately notice the difference in the bass, more texture, sounds fuller and a little bit more punchy, as well as overall resolution and imaging
• Bass has got more punch compared to Angel’s internal amp
• Treble is lively and nuances can be picked up easily, analytical yet enjoyable at the same time

Pairing impression with various Transducers
Final Audio Heaven II

• Heaven II is a single BA IEM and the tonality is slightly on the warm side and bass lacks a little extension due to it being a single BA
• Pairing it with the ST-Amp, somehow the bass sounds fuller and has a bit more extension, the treble also have slightly better extension to it
• Soundstage and imaging is improved a little as well

Hidizs MS5

• MS5 has very low impedance and quite picky in terms of source, i have paired it with iFi’s Gryphon, Go Blu, XA-10, and they all hiss whenever i plug it into the 4.4 port, I’m very surprised when i plug it into 4.4 port of ST-AMP, it doesn’t hiss
• Bass sounds fuller and good punch, treble on MS5 for certain song have slight sibilance, with ST-Amp, it seems to be very well under controlled and kept at minimum (bearable level for my listening preference)
• Precise imaging as well as slightly bigger soundstage

Kiwi Ears Orchestra Lite

• Despite being a full BA set, it doesn’t exhibit any noise or hiss when i plug it i
• Orchestra Lite is another set that’s safe sounding by nature, pairing it with the ST-Amp seems to be a great choice, the dynamics are improved and it is certainly a little more fun sounding now
• Bass is tight and well controlled, sounds fuller as well
• Detail retrieval and staging is excellent

Kiwi Ears Quartet

• A hybrid set with 2DD and 2BA config, default dip switch configuration, bass is fast and tight, full and sub bass has good extension as well
• Treble doesn't sound harsh
• Very good imaging and soundstage
• ST-Amp somehow makes whatever that’s plugged into it sounds good

Final Thoughts
My experience with Earmen’s product has been good, ST-Amp is no exception. As a Dac/Amp combo, although the in-built DAC is not a high performance DAC, it provides good enough sonic performance for users who are conscious about desk space.
However, the strength of ST-Amp lies in the amp itself, it is very clean and packs enough punch for most IEMs and efficient headphones out there.

The overall build quality is solid and it certainly looks like it is built to last. With all that being said, there are some drawbacks such as the lack of gain switch, as well as bundled accessories (nitpicking)

Still, without any doubt, I absolutely recommend the ST-Amp for those who are looking for a clean and dynamic sounding dac/amp.

Head to the link below if you are interested in getting a unit yourself
Earmen ST-Amp- Non affiliated
Earmen ST-Amp Product Page

The EarMen ST-Amp was kindly provided free of charge in exchange for an honest review.
I didn't receive monetary or any other kind of compensation and I don't use affiliate links.
The EarMen ST-Amp retails for $599 or €599 and you can order it from the EarMen online shop.



EarMen ST-Amp

EarMen are mostly known for some of the best sounding portable headphone DAC/amps like the Colibri or the Angel but lately they have also been expanding to include desktop devices like the CH-Amp.
The EarMen ST-Amp is the latest addition to the family, a fully balanced desktop headphone amplifier with a preamplifier option and an integrated DAC.

Technical specifications

The amplifier is fully balanced and moreover the exact same topology is used for single ended signals, so they become balanced in a special way with almost no phase shift, additional noise or THD, so the sound from the SE output does not lag behind the sound from the balanced output.
The headphones outputs are powered by two TPA6120 operational amplifiers, which have proven to be excellent in the audiophile world.
To make the experience complete, a high-quality balanced ALPS potentiometer is used for greater sound transparency.
The power output of the 6.35mm jack is 4VRMS - 0.5W/32Ω and that of the 4.4mm jack is 7.75VRMS - 1.85W/32Ω, plenty to drive most headphones.



The digital to analog conversion is handled by a single ES9280 DAC chip by ESS technology and supports PCM up to 384 kHz and DSD128 while MQA decoding is not supported.

At the heart of the device itself is a noiseless linear power supply with great stability, so it can easily provide enough power even for the most demanding headphones.
Apart from the special topology of the amplifier, the power supply is worthy of excellent characteristics even at full power, which is often not the case with most amplifiers, so in their specifications you can find measurements but at half power.



User interface

On the back panel of the device there are both single ended and balanced line level inputs and pre-outputs.
So the ST-Amp can be used as a headphone amplifier and a preamplifier both from the embedded DAC and the line inputs to accommodate different use scenarios.
The user can't bypass the volume control and use it as a fixed line output.
To keep size as compact as possible, EarMen have opted to use 4.4mm jacks instead of 3-pin XLR while the digital inputs are limited to a USB type B plug.
At the front face there are two switches, one for powering on/off and the other for selecting between the digital or the analogue inputs.
The center is dominated by the large aluminum knob of the potentiometer, which has excellent feedback, and next to it there are the two headphone outputs, 4.4mm balanced and 6.35mm single ended.

Build quality and appearance

The EarMen ST-Amp measures just 170x30x150mm so it is compact enough to fit virtually everywhere without occupying too much space, you can place it at your desk combined with a PC or at a bedside table with your phone as a source.
The chassis is made from thick aluminum that also acts as an EMI shield but the appearance is rather ordinary and industrial, the ST-AMP reminds more of studio gear rather than a luxurious home appliance.
Build quality and finish are excellent but the chassis has sharp corners and it is a little unstable because there are only three rubber feet underneath rather than the usual four.
This is a high-end approach that is regularly used in larger devices because it offers better vibration isolation but in the compact sized ST-Amp, where you frequently plug and unplug headphones, it doesn't work very well.



Power output and associated gear

The EarMen ST-Amp was left playing music for about 100 hours in order to settle down.
I have used a variety of headphones like the Focal Clear Mg, HiFiMan XS, Sennheiser HD660S2 and Meze 109 PRO both from the balanced and the single ended outputs.
All the headphone cables are of pure silver made by Lavricables.
External sources for testing the analogue inputs included the iBasso DX320/AMP14, Cayin N7, Aune X8 XVIII and the FiiO R7.

The claim of EarMen that the sound quality of the single ended output is very close to that of the balanced is true indeed but it should be noted that the balanced has the lead with more openness, better holography, sharper imaging, increased technicalities and greater dynamic impact.

The EarMen ST-Amp is powerful enough and will not have a problem driving most of the headphones minus some very inefficient ones.
The noise floor is barely audible, the amplifier is very silent with a black background that makes it suitable for use with sensitive earphones and helps a lot with detail retrieval, allowing for the finest nuances to emerge from the depths of the recording.
Of course there are more powerful headphone amplifiers at this price point but given that the TPA6120 is used, the EarMen ST-Amp power output is at the top limit of what this particular op-amp can provide as it maxes at 8V - 2W/32Ω for a balanced configuration.



Listening impressions - Headphone amplifier

You can use the EarMen ST-Amp either as a standalone headphone amplifier with a source of your choice or as an all-in-one DAC/amp through the USB input.
And while the embedded DAC is an easy to use and very good sounding solution when nothing else is available, it is the headphone amplifier that is the main feature of the ST-Amp and it really shines with a source of higher quality than that of the internal DAC.

The audio performance of the headphone amplifier is truly exceptional, the EarMen ST-Amp is linear and transparent with uncompromised source fidelity while at the same time it manages to present a balanced, natural and organic sound signature with plenty of realism and harmonic intensity.
The sound is full bodied with a weighty and impactful bass that has excellent control, it is fast, tight, and well defined with deep layering and very contrasted dynamics that add great realism to more demanding material like large scale symphonic works.
This recent cycle of the Carl Nielsen symphonies sounded really enjoyable and glorious with the Meze Elite driven by the EarMen ST-Amp and fed by the Cayin N7 line-out.



The mid range is very open sounding and articulated with plenty of harmonic variety and natural timbre, it sounds musical, engaging and emotionally involving with great tonal balance and a touch of warmness.
The treble is transparent and energetic, the amplifier is not short of extension but it doesn't induce any brightness or emphasis.
Detail retrieval is very satisfying while the EarMen ST-Amp doesn't sound analytical or artificial.
The truth is that the EarMen ST-Amp features one of the best implementations of the humble and commonly used TPA6120 op-amp with an audio performance that is more analogue sounding and less artificial than in some THX implementations of the same chip.
It may not sound as detailed, transparent, refined and resolving as its THX counterparts but it presents the music in a more expressive and communicative way, something that works very well with classical and jazz.
Still, the EarMen ST-Amp is very good with every other music genre but there is the chance that someone might prefer a more sparkling and luminous presentation that THX amplifiers can offer.



Listening impressions DAC/amp

In the case that you need to add more energy and brio to the sound, you may use the internal DAC which offers more agility and sharpens, it is a touch brighter and leaner than the standalone amplifier, less warm and smooth so it may better suit certain headphones or types of music.
The basic sonic qualities remain, more or less the same and close enough to the amplifier performance but you lose some of the timbre naturalness and the analogue character of the sound.
There is a difference also in the soundstage presentation, the amplifier can sound very holographic and immersive, given that a potent source is used, when the internal DAC can't compete at the same level.
You don't have to use something expensive, the combination of the Aune X8 XVIII DAC with the ST-Amp sounded better than the internal DAC when I was listening back and forth to this recent recording of Mahler's second symphony.



Compared to the FiiO K7 with the FiiO PL50 ($350 total)

The FiiO K7 is a fully balanced DAC/amp all-in-one desktop device without an internal linear power supply but you can add the FiiO PL50 external LPS to enhance the performance.
The FiiO K7 and PL50 combination is $350 so it is a whole $250 cheaper than the EarMen ST-Amp but you are buying two devices that occupy more real estate than the ST-Amp while they are not so visually appealing.
The K7 features a balanced headphone amplifier that also uses two TPA6120 op-amps in a THX certified implementation with 2W/32Ω of power output and two gain settings.
The digital conversion is handled by dual AKAK4493S chips with an XMOS dedicated receiver that supports PCM 384kHz-32bit and DSD256.
Except for the USB input, the K7 has coaxial and optical digital inputs so it is more versatile but the analogue line inputs and outputs are limited to a single ended RCA and not balanced.
So in this regard, the EarMen ST-Amp is better suited for use with a really balanced source because it keeps signal integrity without performing any conversion.
Sound performance comparison should be splitted in two sections:
As a DAC/amp, the FiiO K7 offers better sound quality with more natural and organic timbre, better technicalities, more refinement and resolution.
But as a headphone amplifier with an external source, the EarMen ST-Amp is definitely the leader by a fair margin.
The sound has more analogue and organic qualities to it, the timbre is considerably more natural, the soundstage is grander and more holographic with sharper imagining and the overall technicalities are a step above that of the FiiO K7.
The EarMen ST-Amp is also better as an analogue preamplifier for driving powered monitors especially if a balanced path is desired.
It would be fair to conclude that the EarMen ST-Amp is an excellent headphone amplifier with a DAC as an extra complementary feature while the FiiO K7 is an excellent DAC/amp with an analogue input/output as a bonus.



In the end

The EarMen ST-Amp is an ode to simplicity, it is a proof that a skilled audio engineer can use the most common audio parts to make great sound without having to go discrete or improvise exotic topologies.
There are so many competitive products that use the same op-amps with the EarMen ST-Amp but few of them can sound equally good, at least in the pure amplification stage.
The EarMen ST-Amp is an excellent sounding headphone amplifier and analogue preamplifier that can also double as a DAC/amp when a better source is not available while it is compact enough to fit virtually everywhere.
Straight and simple, the EarMen ST-Amp is one of the best balanced headphone amplifiers in its respective category.

Test playlist

Copyright - Petros Laskis 2023.