Audio T Verdict
The EarMen ST-Amp is a neat answer to the question of how much proper desktop Hi-Fi can be squeezed into a genuinely compact chassis. It combines a USB DAC, fully balanced headphone amplifier and variable analogue pre-amplifier in a box measuring just 170 x 150 x 30mm.
Its headphone section is the star of the show. Two Texas Instruments TPA6120 amplifier stages provide a conventional 6.35mm output capable of 0.5W into 32 ohms and a much more powerful balanced 4.4mm connection delivering up to 1.85W into the same load.
The internal ESS ES9280 DAC supports PCM at up to 384kHz, DXD at 352.8 and 384kHz and DSD64 or DSD128 through DoP. A rear USB connection therefore allows a computer or compatible mobile device to form a complete digital headphone system without adding a separate DAC.
Unlike many DAC/headphone amplifiers, the ST-Amp can also work entirely in the analogue domain. RCA and balanced 4.4mm inputs allow an existing DAC, CD player, streamer or phono stage to use the ST-Amp purely as an amplifier.
Both RCA and balanced 4.4mm variable pre-outs are provided as well, so the same volume control can feed active speakers or a suitable stereo power amplifier.
The fully balanced architecture, balanced ALPS volume control and internal low-noise linear power supply make this considerably more serious than a USB soundcard with a headphone socket attached.
There are sensible limitations. USB is the only digital input, there is no Bluetooth, optical or coaxial connection, there is no remote control and MQA is not supported. But for a desk, home office or compact headphone system where USB and analogue sources cover the requirements, the ST-Amp packs an impressive amount of functionality into a remarkably small footprint.
EarMen ST-Amp Desktop DAC and Headphone Amplifier
The EarMen ST-Amp combines three functions within one compact aluminium chassis:
- USB digital-to-analogue converter
- Fully balanced headphone amplifier
- Variable analogue pre-amplifier
It can therefore form the centre of a dedicated headphone setup, a compact computer-audio system or a small speaker system using active loudspeakers or external power amplification.
Key features include:
- ESS ES9280 DAC
- Fully balanced amplifier architecture
- Two TPA6120 headphone amplifier stages
- Balanced ALPS volume potentiometer
- USB digital audio input
- RCA analogue input
- 4.4mm balanced analogue input
- 6.35mm single-ended headphone output
- 4.4mm balanced headphone output
- 0.5W into 32 ohms single-ended
- 1.85W into 32 ohms balanced
- RCA variable pre-amplifier output
- 4.4mm balanced variable pre-amplifier output
- PCM playback up to 384kHz
- DXD playback at 352.8 and 384kHz
- DSD64 and DSD128 through DoP
- Internal low-noise linear power supply
- Aluminium construction
- Compact desktop dimensions
ESS ES9280 DAC
Digital-to-analogue conversion is handled by the ESS ES9280.
The integrated DAC allows the ST-Amp to connect directly to a compatible computer, smartphone or tablet without requiring another conversion component between the source and amplifier.
Supported digital audio includes:
- PCM up to 384kHz
- DXD at 352.8kHz
- DXD at 384kHz
- DSD64 through DoP
- DSD128 through DoP
The maximum format available in practice depends on the source device, operating system, driver and playback application.
PCM Up to 384kHz
The ST-Amp accepts PCM digital audio at sample rates up to 384kHz.
This covers the overwhelming majority of conventional digital music including:
- CD-quality 16-bit/44.1kHz audio
- FLAC
- WAV
- AIFF
- Apple Lossless
- High-resolution music downloads
- Lossless streaming from compatible computer applications
There is no requirement to use extremely high sample rates for the ST-Amp to provide a worthwhile upgrade over the audio circuitry built into a typical computer.
DSD64 and DSD128
DSD64 and DSD128 are supported through DoP.
DoP packages DSD data within a PCM-compatible transport structure so that it can be sent through the USB audio connection without converting the underlying DSD content to conventional PCM.
A compatible source, driver and playback application are required.
DXD Playback
The ST-Amp also supports DXD at 352.8kHz and 384kHz.
DXD is encountered mainly with specialist high-resolution recordings and production workflows, but its support demonstrates the available bandwidth of the ST-Amp's digital section.
No MQA Support
The EarMen ST-Amp does not provide MQA decoding or MQA rendering.
This differentiates it from some other EarMen DACs that were designed with MQA support.
Current lossless FLAC streaming from services such as TIDAL does not require MQA hardware and is handled as conventional PCM audio.
USB Digital Audio Input
A rear USB connection provides the ST-Amp's digital input.
It allows a compatible computer or mobile device to send digital music directly to the internal ESS DAC.
EarMen documents compatibility with:
- Windows 10
- Windows 11
- macOS
- Android
- Apple iOS
The appropriate USB cable or mobile-device adaptor will depend on the source being used.
USB-B Desktop Connection
The rear USB input uses the conventional desktop USB connection rather than the USB-C socket found on EarMen's portable DACs.
This makes the ST-Amp particularly suited to a permanent computer-audio installation.
An appropriate USB cable or adaptor is required when connecting smartphones and tablets.
Digital or Analogue Operation
A front-panel switch selects between digital and analogue sources.
Choose:
- D: for the internal USB DAC
- A: for the rear analogue inputs
This allows the ST-Amp to work either as a complete USB DAC/headphone amplifier or purely as an analogue headphone amplifier with another source.
RCA Analogue Input
A conventional stereo RCA input allows an external analogue source to bypass the internal DAC.
Suitable sources include:
- Standalone DAC
- Network streamer with analogue output
- CD player
- Phono stage
- Tuner
- Other line-level source equipment
EarMen specifies 2V input sensitivity for the single-ended input.
A Turntable Needs a Phono Stage
The RCA connection is a conventional line-level input rather than a moving magnet or moving coil phono input.
A turntable cartridge therefore requires a suitable external phono stage before connection to the ST-Amp.
4.4mm Balanced Analogue Input
A rear 4.4mm Pentaconn socket provides balanced analogue input.
EarMen specifies 4V input sensitivity for this connection.
It can be used with compatible balanced DACs and source components while maintaining balanced operation through the ST-Amp.
Balanced Input Takes Priority
When analogue mode is selected, the ST-Amp automatically chooses between its RCA and balanced inputs.
If a 4.4mm balanced plug is inserted into the rear balanced input, the RCA input becomes inactive.
Switching Between Two Analogue Sources
The RCA and 4.4mm inputs are not two independently selectable analogue inputs.
The 4.4mm connection takes priority whenever a balanced plug is inserted.
To listen to the RCA input, remove the balanced 4.4mm input connection.
Fully Balanced Amplifier Architecture
The headphone amplifier uses a fully balanced topology.
EarMen also processes incoming single-ended signals using the same basic balanced amplifier architecture rather than treating the RCA path as an unrelated lower-specification circuit.
A properly implemented balanced design can provide advantages including:
- Higher available output voltage
- Greater headphone power
- Improved channel separation
- Reduced common-mode interference
- Greater dynamic headroom
Balanced operation should not automatically be assumed to sound better with every headphone, but it does provide significantly more available power from the ST-Amp.
Twin TPA6120 Headphone Amplifier Stages
Two Texas Instruments TPA6120 high-speed amplifier stages are used within the headphone section.
The design is intended to combine substantial output capability with low noise and distortion while remaining stable with a range of headphone loads.
Balanced ALPS Volume Control
A high-quality balanced ALPS potentiometer provides physical volume adjustment.
This controls both headphone listening and the variable rear pre-amplifier outputs.
The analogue control also means volume remains directly accessible without relying on a computer application or touchscreen.
6.35mm Headphone Output
A conventional 6.35mm headphone socket accommodates the full-size single-ended jack found on many domestic Hi-Fi headphones.
EarMen specifies:
- Maximum output voltage of approximately 4Vrms
- 0.5W into 32 ohms
- THD+N from approximately 0.0025%
- Signal-to-noise ratio above 117dB depending on input configuration
- Dynamic range above approximately 117.9dB depending on input configuration
Half a watt is sufficient for a wide range of conventional headphones, although more demanding models can take advantage of the balanced output.
4.4mm Balanced Headphone Output
The 4.4mm Pentaconn headphone connection provides the ST-Amp's highest available output.
EarMen specifies:
- Maximum output voltage of approximately 7.75Vrms
- Up to 1.85W into 32 ohms
- THD+N down to approximately 0.002% depending on input
- Signal-to-noise ratio above 125dB with balanced input
- Dynamic range above 126dB with balanced input
The substantial increase in output makes the balanced connection particularly useful with lower-sensitivity headphones and many planar magnetic designs.
Use a Proper Balanced Headphone Cable
The 4.4mm output should only be used with headphones correctly wired for balanced operation.
Do not use an unsuitable adaptor that joins the negative amplifier outputs together to create a conventional single-ended connection.
Use the dedicated 6.35mm output for single-ended headphones.
Only One Headphone Output Operates at a Time
The ST-Amp does not operate its two headphone outputs simultaneously.
If a plug is inserted into the 6.35mm single-ended socket, the balanced headphone output is inactive.
To listen through the 4.4mm balanced output, remove anything connected to the 6.35mm socket.
Balanced Output Not Working?
Check the 6.35mm headphone socket first.
If a headphone plug or adaptor remains connected there, the balanced output will not operate.
0.5W Single-Ended Output
The 6.35mm output delivers up to approximately 0.5W into a 32-ohm headphone load.
This provides significantly more output than a typical laptop or smartphone headphone connection and should be suitable for many conventional dynamic headphones.
1.85W Balanced Output
The 4.4mm connection increases maximum output to approximately 1.85W into 32 ohms.
This additional power can be particularly valuable with:
- Lower-sensitivity headphones
- Many planar magnetic headphones
- Headphones requiring greater dynamic headroom
- Recordings mastered at relatively low levels
Maximum power alone does not determine headphone compatibility. Impedance, sensitivity and required listening level all matter.
Using the ST-Amp with Planar Magnetic Headphones
The balanced output's 1.85W rating makes the ST-Amp suitable for many planar magnetic headphones.
Some specialist planar designs remain exceptionally demanding, so a demonstration with the actual headphones is worthwhile where possible.
Using the ST-Amp with Sensitive Headphones
Efficient headphones do not require anything close to the ST-Amp's maximum output.
Always begin with the volume turned down before connecting sensitive headphones or in-ear monitors.
The ST-Amp does not provide a separate low/high gain switch, so usable volume-control range should be checked with exceptionally sensitive earphones.
No Gain Switch
Unlike the EarMen Angel and CH-Amp, the ST-Amp does not provide selectable low and high gain settings.
Output level is controlled using the front balanced ALPS volume potentiometer.
This keeps operation simple but makes a demonstration particularly useful with extremely sensitive in-ear monitors.
RCA Pre-Amplifier Output
A variable stereo RCA pre-output allows the ST-Amp to control another amplifier or active speaker system.
The output level is adjusted using the same front volume control used for headphone listening.
This allows the ST-Amp to form the control centre of a compact desktop speaker system.
4.4mm Balanced Pre-Amplifier Output
A balanced 4.4mm pre-output is also provided.
This enables a balanced connection to compatible active speakers or power amplification using an appropriate interconnect.
The 4.4mm format keeps the chassis compact while providing separate balanced signal paths without requiring the space occupied by a pair of full-size XLR sockets.
Using the ST-Amp with Active Speakers
The variable pre-outs allow a compact system to be assembled from:
- Computer or analogue source
- EarMen ST-Amp
- Active loudspeakers
The ST-Amp then handles digital conversion where required, analogue source selection and listening volume.
Use the RCA or balanced pre-output according to the connections available on the speakers.
Using the ST-Amp with a Power Amplifier
The ST-Amp can also function as a compact stereo pre-amplifier feeding a suitable power amplifier.
This creates a small separates system while retaining dedicated headphone capability.
Reduce Volume Before Connecting a Power Amplifier
The rear pre-outs are variable and controlled by the ST-Amp's front volume control.
Begin with volume fully reduced when connecting active loudspeakers or power amplification and increase it gradually.
Check the input sensitivity of the connected equipment before use.
Using an External DAC
The presence of an internal DAC does not prevent a higher-performance or differently voiced external DAC being used.
Connect the external DAC's analogue output to either:
- The RCA analogue input
- The balanced 4.4mm analogue input
Then select analogue mode from the front panel.
The ST-Amp will operate purely as a headphone amplifier and pre-amplifier.
Internal Linear Power Supply
The ST-Amp contains its own low-noise linear power supply rather than relying on USB bus power or an external plug-top adaptor.
This provides the headphone amplifier with a stable local power source independent of the computer's USB supply.
The rear panel therefore includes a conventional mains inlet together with a voltage selector.
Mains Voltage Selector
The rear voltage selector must correspond to the local mains supply before the ST-Amp is connected to power.
Check the Voltage Selector Before Use
Do not connect the ST-Amp to mains power until the voltage selector is correctly configured for the local electrical supply.
UK units should normally already be configured appropriately by the authorised retailer, but the setting should still be checked if there is any doubt about the product's history.
No Pop or Click on Power-Up
EarMen has designed the headphone amplifier to minimise unpleasant switching noises when powering the ST-Amp on or off.
As a matter of good practice, however, Audio T still recommends reducing volume before powering equipment or changing headphones.
No Optical or Coaxial Digital Inputs
The ST-Amp has one digital-audio route: USB.
It does not contain:
- Optical Toslink input
- Coaxial S/PDIF input
- AES/EBU input
- HDMI input
A CD transport or network streamer with digital-only optical or coaxial outputs therefore requires another DAC before connection to the ST-Amp's analogue input.
No Bluetooth or Network Streaming
The ST-Amp is not a wireless music player.
There is no:
- Bluetooth
- Wi-Fi
- Ethernet
- Spotify Connect
- TIDAL Connect
- Qobuz Connect
- AirPlay
- Network music browser
A connected computer, mobile device or separate streamer handles music browsing and streaming-service access.
Using TIDAL, Qobuz and Other Streaming Services
Online streaming services can still be used through the USB DAC.
Run the required application on the connected computer or compatible mobile device, then select the ST-Amp as the USB audio output.
This allows playback from services such as:
- Qobuz
- TIDAL
- Apple Music
- Spotify
- Amazon Music
The maximum output resolution depends on the service, subscription tier, operating system and playback software.
ST-Amp or CH-Amp?
Choose the ST-Amp When
- An integrated USB DAC is required
- One compact chassis is preferred
- 1.85W balanced output is sufficient
- Computer audio forms the main digital source
- RCA and balanced analogue inputs cover your sources
- Pre-amplifier outputs are required
- A lower overall system cost is desirable
Choose the CH-Amp When
- You already own a suitable DAC
- Maximum headphone power is important
- Up to 3.8W balanced output is useful
- Multiple analogue RCA inputs are required
- Low and high gain settings are useful
- Remote control is important
- The separate PSU-3 linear supply appeals
The EarMen CH-Amp is the more powerful dedicated analogue headphone amplifier, while the ST-Amp provides the convenience of its own USB DAC.
ST-Amp or Angel?
Choose the ST-Amp When
- The amplifier will remain on a desk or Hi-Fi rack
- Mains power is preferable to battery operation
- Analogue inputs are required
- A 6.35mm headphone connection is preferred
- 1.85W balanced headphone output is useful
- A conventional desktop volume control is preferred
- Active speakers or a power amplifier will be connected
Choose the Angel When
- Portable battery operation is required
- USB-C connectivity is preferred
- Optical or coaxial digital sources need connecting
- Native DSD512 is required
- MQA hardware decoding remains useful for legacy files
- 4.4mm portable headphone operation is the priority
The EarMen Angel provides a more portable approach with rechargeable battery power and broader digital compatibility.
ST-Amp or Tradutto and CH-Amp?
Choose the ST-Amp When
- One compact product is preferred
- USB is the principal digital source
- A simple desktop system is wanted
- Separate DAC upgrades are unlikely
- 1.85W balanced output covers your headphones
- Value and simplicity matter
Choose Separate EarMen Components When
- You want a more ambitious modular system
- The Tradutto's broader digital connectivity is useful
- Bluetooth reception is required
- The CH-Amp's greater headphone power is useful
- Individual component upgrades are important
- The PSU-3 power architecture appeals
The EarMen Tradutto DAC and CH-Amp form the more modular alternative for customers wanting to separate conversion and amplification.
System Matching
Well Suited To
- Windows PCs
- Mac computers
- Compatible USB smartphones and tablets
- Full-size Hi-Fi headphones
- 4.4mm balanced headphones
- Many planar magnetic headphones
- External DACs
- CD players with analogue outputs
- Network streamers with analogue outputs
- Phono stages
- Active loudspeakers
- Stereo power amplifiers
- Compact desktop systems
Check Before Buying
- USB is the only digital input
- No optical input
- No coaxial digital input
- No Bluetooth
- No Wi-Fi or network streaming
- No MQA support
- No remote control
- No selectable gain
- Only one headphone output is active at a time
- The balanced analogue input takes priority over RCA
- Turntables require a separate phono stage
- Very demanding headphones may benefit from the CH-Amp
Placement and Setup
The ST-Amp should be installed on a solid, level and stable surface.
Although its chassis is compact, avoid covering the unit or placing it directly against other heat-producing equipment.
The mains inlet should remain accessible and the voltage selector should be checked before initial installation.
Connection Guidance
- Reduce volume before connecting or changing headphones.
- Select Digital when using the internal USB DAC.
- Select Analogue when using RCA or balanced analogue input.
- Remove the balanced analogue input plug if you want to use the RCA input.
- Remove anything from the 6.35mm headphone output when using the 4.4mm balanced headphone connection.
- Use a properly wired 4.4mm cable for balanced headphones.
- Do not use an unsuitable adaptor that shorts balanced outputs together.
- Use a proper USB data cable for computer audio.
- A turntable requires an external phono stage.
- Reduce volume before connecting active speakers or a power amplifier.
- Check the rear mains-voltage selector before connecting power.
- Allow reasonable ventilation around the amplifier.
Key Features
- Desktop DAC
- Headphone amplifier
- Analogue pre-amplifier
- Fully balanced amplifier architecture
- ESS ES9280 DAC
- Twin TPA6120 headphone amplifier stages
- Balanced ALPS volume potentiometer
- USB digital audio input
- RCA analogue input
- 4.4mm balanced analogue input
- 2V single-ended input sensitivity
- 4V balanced input sensitivity
- 6.35mm headphone output
- 4.4mm balanced headphone output
- 4Vrms single-ended output
- 0.5W into 32 ohms single-ended
- 7.75Vrms balanced output
- 1.85W into 32 ohms balanced
- THD+N from approximately 0.002%
- Signal-to-noise ratio above 125dB in optimal balanced configuration
- Dynamic range above 126dB in optimal balanced configuration
- RCA variable pre-output
- Balanced 4.4mm variable pre-output
- PCM playback up to 384kHz
- DXD at 352.8kHz
- DXD at 384kHz
- DSD64 through DoP
- DSD128 through DoP
- Windows 10 compatibility
- Windows 11 compatibility
- macOS compatibility
- Android compatibility
- Apple iOS compatibility
- Digital and analogue source selector
- Internal linear power supply
- Mains-voltage selector
- Aluminium chassis
- 170mm depth
- 150mm width
- 30mm height
- Approximately 1.1kg weight
- Two-year manufacturer warranty subject to EarMen terms
Frequently Asked Questions
What is the EarMen ST-Amp?
It is a compact fully balanced desktop USB DAC, headphone amplifier and variable analogue pre-amplifier.
Does the ST-Amp contain a DAC?
Yes. It uses the ESS ES9280.
Can I use it without the internal DAC?
Yes. RCA and balanced 4.4mm analogue inputs allow an external DAC or another analogue source to feed the headphone amplifier directly.
Which digital inputs does it have?
USB is the ST-Amp's digital audio input.
Does it have optical input?
No.
Does it have coaxial digital input?
No.
Does it have Bluetooth?
No.
Does it have Wi-Fi or network streaming?
No.
Which DAC chip does it use?
The ESS ES9280.
What is the maximum PCM resolution?
PCM is supported at up to 384kHz.
Does it support DSD?
Yes. DSD64 and DSD128 are supported through DoP.
Does it support native DSD512?
No. The EarMen Angel provides substantially greater DSD capability.
Does it support DXD?
Yes. DXD at 352.8kHz and 384kHz is supported.
Does it support MQA?
No. MQA decoding and rendering are not specified for the ST-Amp.
Can I still use TIDAL?
Yes. Run TIDAL on the connected computer or mobile device and send its digital audio to the ST-Amp through USB. Current TIDAL lossless and high-resolution stereo playback uses FLAC rather than MQA.
Can I use Qobuz?
Yes. Qobuz can run on the USB-connected source device.
Can I use Spotify?
Yes, through the connected computer or mobile device. The ST-Amp does not contain Spotify Connect itself.
Does it have a 6.35mm headphone socket?
Yes.
Does it have balanced headphone output?
Yes. A 4.4mm Pentaconn balanced connection is provided.
How powerful is the 6.35mm output?
EarMen specifies approximately 4Vrms and 0.5W into 32 ohms.
How powerful is the balanced output?
EarMen specifies approximately 7.75Vrms and 1.85W into 32 ohms.
Can both headphone outputs be used simultaneously?
No. Only one headphone output operates at a time. The 6.35mm connection takes priority, so it must be disconnected before the 4.4mm balanced output can operate.
Can it drive planar magnetic headphones?
Its 1.85W balanced output is suitable for many planar magnetic headphones. Particularly insensitive models should be demonstrated to confirm sufficient headroom.
Can it drive sensitive IEMs?
Potentially, although the ST-Amp has no selectable gain setting. Very sensitive earphones are worth demonstrating to ensure the available volume-control range is appropriate.
Does it have low and high gain?
No. Gain is not user selectable.
Does it have analogue input?
Yes. One stereo RCA input and one balanced 4.4mm input are provided.
Can both analogue inputs remain connected?
They can physically remain connected, but inserting a plug into the balanced 4.4mm input disables the RCA input. Remove the balanced connection when you want to listen through RCA.
Can I connect a turntable?
Yes, but a suitable external phono stage is required because the ST-Amp does not contain a phono input.
Can I connect a CD player?
Yes, through the CD player's analogue RCA output. A CD transport with digital-only output requires a suitable external DAC first.
Can I connect a network streamer?
Yes, provided the streamer has a compatible analogue output. A USB-capable digital source may alternatively use the ST-Amp's internal DAC.
Does it work as a pre-amplifier?
Yes. Both RCA and balanced 4.4mm variable pre-amplifier outputs are provided.
Can I connect active speakers?
Yes, provided the active speakers have a compatible analogue input.
Can I connect a stereo power amplifier?
Yes. The ST-Amp can control a compatible power amplifier using its variable RCA or balanced pre-output.
Does it have a fixed DAC line output?
The documented rear outputs are variable pre-amplifier outputs controlled by the front volume control rather than a separate dedicated fixed-level DAC output.
Does it have a remote control?
No remote control is specified for the ST-Amp.
Does it contain an external power supply?
No external plug-top power supply is required for normal operation. The ST-Amp contains its own linear power supply and connects directly to mains power.
Why does it have a voltage selector?
The selector configures the internal power supply for the appropriate mains-voltage range. It must be correctly set before power is connected.
Does it run from USB power?
No. USB carries digital audio, while the ST-Amp's amplifier and DAC circuitry are powered from its internal mains power supply.
Does it work with Windows?
Yes. EarMen documents Windows 10 and Windows 11 compatibility.
Does it work with Mac?
Yes. macOS is supported.
Can it be used with Android?
Yes, with a compatible USB connection or adaptor.
Can it be used with iPhone or iPad?
Yes, with the appropriate USB connection or Apple-compatible adaptor for the particular device.
How large is it?
Approximately 170 x 30 x 150mm.
How much does it weigh?
Approximately 1.1kg.
Is it smaller than the CH-Amp?
The two products occupy similarly compact desktop footprints, but the ST-Amp combines its DAC, headphone amplifier and mains power supply in one chassis, whereas the CH-Amp is a dedicated analogue amplifier supplied with the separate PSU-3.
What is the warranty?
EarMen provides a two-year limited manufacturer warranty, subject to product registration, proof of purchase and the company's current warranty conditions.
Related EarMen Products and Audio T Guides
Why Buy From Audio T?
- EarMen ST-Amp demonstrations
- Headphone and earphone matching advice
- Balanced and single-ended headphone comparisons
- Planar magnetic headphone matching
- USB computer-audio setup
- Windows and Mac configuration advice
- External DAC comparisons
- High-resolution PCM and DSD setup guidance
- Active-speaker integration
- Stereo power-amplifier integration
- Balanced 4.4mm cable advice
- Comparison with the EarMen Angel and CH-Amp
- Ongoing setup and after-sales support
Contact your local Audio T store to arrange a demonstration or discuss matching the EarMen ST-Amp with your headphones, computer, DAC, active speakers or existing Hi-Fi system.