EarMen ST-Amp Review
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 store
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.
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.
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 , 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.
Copyright – Petros Laskis 2023.
+ Expressive and organic sound signature
+ Natural timbre without artificiality
+ Dynamic and impactful bass with great technicalities
+ Smooth but not subdued treble
+ Crystal clear and transparent
+ Fully balanced design
+ Single ended output is not gimped
+ Exceptionally low noise floor
+ Powerful headphone amplifier
+ Very good analogue preamplifier
+ Internal linear power supply
+ Compact sized
– Ordinary appearance
– The chassis has sharp corners
– No coaxial or optical inputs
– No gain settings
– The internal DAC performance is not up to the headphone amplifier standards
– DSD is limited to 128 and no MQA decoding
– A little unstable placement
– Lack of accessories