Audio T Verdict
The EarMen CH-Amp is a deceptively compact headphone amplifier. Its 150mm-square chassis may look more like a small desktop accessory than serious Hi-Fi electronics, but internally it is a fully balanced analogue amplifier capable of delivering up to 3.8W into 32 ohms through its 4.4mm balanced headphone output.
Unlike many modern headphone amplifiers, the original CH-Amp deliberately contains no DAC or digital inputs. Instead, EarMen concentrates on taking the analogue output from a DAC, streamer, CD player or other source and amplifying it cleanly through either conventional RCA or balanced 4.4mm connections.
There is plenty of flexibility. Two single-ended RCA inputs are joined by a balanced 4.4mm input, while the front panel provides both a conventional 6.35mm headphone socket and balanced 4.4mm output. Low and high gain settings make it easier to match headphones with very different sensitivity and power requirements.
The balanced connection is particularly capable, providing up to 11Vrms and 3.8W into 32 ohms in high gain. The 6.35mm output is hardly an afterthought either, with up to 7Vrms and 1.5W into 32 ohms.
The CH-Amp also doubles as a proper analogue pre-amplifier. Remove the headphones and its single-ended RCA and balanced 4.4mm pre-outs become active, allowing it to control active speakers or a suitable power amplifier.
A substantial external PSU-3 linear power supply is included rather than being an optional upgrade. It separates the mains transformer and associated power circuitry from the sensitive headphone amplifier and can also supply compatible EarMen Tradutto and Staccato components as part of a complete desktop system.
Add the OLED display, rechargeable remote control, aluminium construction and excellent connectivity and the CH-Amp becomes much more than a headphone socket in a small box. For listeners who already own a DAC and want a powerful, flexible analogue headphone amplifier with proper pre-amplifier functionality, it remains a very appealing desktop solution.
EarMen CH-Amp Headphone Amplifier and Pre-Amplifier
The EarMen CH-Amp is a fully balanced desktop headphone amplifier and analogue pre-amplifier supplied with EarMen's separate PSU-3 low-noise linear power supply.
It is designed for customers who already have a suitable analogue source or DAC and want substantially more headphone-driving ability, balanced operation and the flexibility to control active speakers or external power amplification.
Key features include:
- Fully balanced analogue architecture
- Composite amplifier topology
- SoundPlus OPA1642 operational amplifiers
- WIMA capacitors
- MELF low-noise resistors
- Two RCA single-ended analogue inputs
- One 4.4mm balanced analogue input
- 6.35mm headphone output
- 4.4mm balanced headphone output
- Up to 1.5W into 32 ohms single-ended
- Up to 3.8W into 32 ohms balanced
- Low and high gain
- Less than 1-ohm headphone output impedance
- RCA pre-amplifier output
- 4.4mm balanced pre-amplifier output
- OLED front display
- Remote volume, input and mute control
- Rechargeable aluminium remote control
- Separate PSU-3 linear power supply included
- PSU-3 can also supply compatible EarMen desktop components
- Compact aluminium construction
Analogue Headphone Amplifier - No Built-In DAC
The original EarMen CH-Amp is an analogue headphone amplifier and pre-amplifier.
It does not contain:
- USB audio input
- Internal digital-to-analogue converter
- Optical digital input
- Coaxial digital input
- Bluetooth
- Wi-Fi
- Network streaming
A DAC, CD player, streamer, phono stage or another source with a suitable analogue output is required.
Original CH-Amp, Not CH-Amp Signature
This product is the original EarMen CH-Amp and should not be confused with the later CH-Amp Signature.
The original CH-Amp concentrates on analogue amplification and requires an external DAC for digital sources.
The newer Signature model adds its own digital-to-analogue conversion and other functionality, but those features do not apply to this product.
Fully Balanced Architecture
The CH-Amp uses a fully balanced amplifier architecture.
When a balanced source is connected through the 4.4mm input, the positive and negative signal phases remain separate through the amplifier to the balanced headphone or pre-amplifier output.
EarMen also converts signals arriving through the single-ended RCA inputs into balanced form within the amplifier.
A balanced design can provide useful benefits including:
- Higher available output voltage
- Greater headphone power
- Improved channel separation
- Reduced susceptibility to common-mode noise
- Greater dynamic headroom
The quality of the complete amplifier circuit remains more important than the connector alone, so balanced operation should not be considered automatically superior with every headphone or source.
Composite Amplifier Topology
EarMen uses a composite amplifier topology within the CH-Amp.
A composite design combines amplifier stages so that the strengths of one stage can compensate for limitations elsewhere in the circuit.
EarMen's objective is to combine good DC accuracy with strong AC performance while reducing changes caused by output-stage loading and temperature.
This is particularly relevant to headphone amplification because impedance and current requirements can vary considerably between different headphone designs.
SoundPlus OPA1642 Operational Amplifiers
Texas Instruments SoundPlus OPA1642 operational amplifiers form part of the CH-Amp's analogue circuitry.
EarMen combines these with carefully selected passive components rather than relying on the amplifier device alone to determine performance.
WIMA Capacitors and MELF Resistors
WIMA capacitors, audio-grade electrolytic capacitors and MELF low-noise resistors are used throughout the signal and supporting circuitry.
The aim is low noise, stable behaviour and consistent performance when the amplifier is driving different headphone loads.
Two RCA Analogue Inputs
Two conventional stereo RCA inputs are provided on the rear panel.
These accept normal line-level analogue sources such as:
- DACs
- CD players
- Network streamers
- Phono stages
- Tuners
- Other line-level source components
EarMen specifies an input sensitivity of 2V for each RCA input.
Turntables Require a Phono Stage
The CH-Amp does not contain a moving magnet or moving coil phono stage.
A turntable cartridge must therefore connect through a suitable external phono stage before entering one of the CH-Amp's RCA line inputs.
4.4mm Balanced Analogue Input
A 4.4mm Pentaconn connection provides the CH-Amp's balanced analogue input.
EarMen specifies 4V input sensitivity for this connection.
It is particularly useful with compact balanced source components such as the matching EarMen Tradutto DAC, where 4.4mm connections allow a complete balanced signal path without requiring full-size XLR sockets.
6.35mm Single-Ended Headphone Output
A conventional 6.35mm headphone socket is provided on the front panel.
This connection accepts the standard full-size jack found on many domestic Hi-Fi headphones without requiring a balanced replacement cable.
In high gain, EarMen specifies:
- Maximum output voltage of 7Vrms
- Maximum output of 1.5W into 32 ohms
- Output impedance below 1 ohm
- THD+N as low as 0.0008%
- Signal-to-noise ratio greater than 116dB
- Frequency response within ±0.005dB
4.4mm Balanced Headphone Output
A balanced 4.4mm headphone connection provides the CH-Amp's highest available output.
In high gain, EarMen specifies:
- Maximum output voltage of 11Vrms
- Maximum output of 3.8W into 32 ohms
- Output impedance below 1 ohm
- THD+N down to approximately 0.0005%
- Signal-to-noise ratio greater than 118dB
- Frequency response within ±0.005dB
The combination of high voltage and substantial power makes the balanced output particularly useful with more demanding full-size headphones.
Use a Proper Balanced Headphone Cable
The 4.4mm balanced headphone output should only be used with headphones wired correctly for balanced operation.
Do not use an adaptor that shorts or joins the negative amplifier outputs together in order to connect a conventional single-ended headphone cable.
Use the dedicated 6.35mm output for conventional single-ended headphones.
Low Gain
Low gain provides a more useful volume-control range with easier-to-drive headphones.
EarMen specifies:
- 2.9V and approximately 260mW into 32 ohms through the 6.35mm output
- 5.5V and approximately 1W into 32 ohms through the balanced 4.4mm output
This setting should normally be tried first, particularly with sensitive headphones.
High Gain
High gain increases the available output for less sensitive or more demanding headphones.
EarMen specifies:
- 7V and up to 1.5W into 32 ohms single-ended
- 11V and up to 3.8W into 32 ohms balanced
Reduce Volume Before Changing Gain
The difference between low and high gain can produce a substantial change in listening level.
Reduce the volume before changing gain and always begin with the lowest gain setting that provides sufficient output.
Less Than 1-Ohm Headphone Output Impedance
Both headphone outputs are specified with an output impedance below one ohm.
A low output impedance helps reduce the amplifier's influence on the frequency response of headphones whose electrical impedance changes across the audible range.
It also improves the CH-Amp's versatility with headphones covering a broad range of nominal impedances.
Using the CH-Amp with Planar Magnetic Headphones
Planar magnetic headphones can place very different demands on an amplifier compared with conventional dynamic models.
The CH-Amp's balanced output of up to 3.8W into 32 ohms makes it well suited to many planar designs, although actual suitability depends on the headphone's sensitivity, impedance and intended listening level.
A demonstration remains worthwhile with particularly demanding headphones.
Using the CH-Amp with High-Impedance Headphones
Maximum amplifier power is not the only important specification when driving headphones.
Higher-impedance designs often require substantial voltage rather than extremely high current.
The CH-Amp's maximum 7Vrms single-ended and 11Vrms balanced output provides considerable voltage headroom for many higher-impedance dynamic headphones.
Using the CH-Amp with Sensitive Headphones
Low gain should normally be selected with easier-to-drive headphones.
This gives a wider useful range on the volume control and reduces the risk of accidentally applying excessive output.
Very sensitive in-ear monitors should ideally be demonstrated before purchase, particularly if extremely low background noise is a priority.
Built-In Analogue Pre-Amplifier
The CH-Amp can also operate as the control centre for a compact speaker system.
When headphones are disconnected, the pre-amplifier outputs become active and the front volume control adjusts the level being sent to the connected equipment.
This allows the CH-Amp to control:
- Active loudspeakers
- Studio monitors
- Stereo power amplifiers
- Another suitable analogue system
Automatic Headphone and Pre-Out Operation
The CH-Amp automatically changes operating behaviour according to whether headphones are connected.
With no headphones inserted, the OLED display shows Pre and the pre-amplifier output is active.
Connecting headphones activates headphone operation instead.
This avoids having speaker and headphone outputs unintentionally operating together.
RCA Pre-Amplifier Output
A conventional stereo RCA pre-output provides single-ended connection to active speakers or power amplification.
EarMen specifies:
- Maximum output level of 4V
- Output impedance of 100 ohms
This is considerably higher than the nominal 2V output of many conventional line-level sources, so always begin with the CH-Amp's volume reduced.
4.4mm Balanced Pre-Amplifier Output
The balanced 4.4mm pre-output allows the CH-Amp to feed compatible balanced equipment while preserving its balanced architecture.
EarMen specifies:
- Maximum output level of 8V
- Output impedance of 200 ohms
A suitable 4.4mm balanced interconnect will be required when connecting equipment that uses XLR or another balanced input format.
Start with the Pre-Amplifier Volume Low
The balanced pre-output can reach 8V and the RCA output can reach 4V.
These are substantial signal levels. Always reduce the CH-Amp's volume before connecting or switching on a power amplifier or active speaker system.
Using the CH-Amp with Active Speakers
The pre-amplifier outputs make it possible to build a compact system without a conventional integrated amplifier.
A typical arrangement might consist of:
- Streamer or computer
- External DAC
- EarMen CH-Amp
- Active loudspeakers
The CH-Amp then handles source selection, volume adjustment and headphone listening.
Using the CH-Amp with a Stereo Power Amplifier
The CH-Amp can also act as an analogue pre-amplifier feeding a suitable stereo power amplifier.
This can create a very compact separates system while retaining dedicated headphone amplification.
Input sensitivity, gain and maximum permissible input voltage of the power amplifier should be checked before connection.
OLED Front Display
A small OLED display provides clear information without dominating the compact front panel.
It displays information including:
- Selected input
- Gain setting
- Volume level
- Pre-amplifier operation
The CH-Amp remembers the previously selected input after it has been switched off.
Volume Control and Mute
The large front control handles volume adjustment and also performs additional functions.
A short press mutes or unmutes the output, while power operation can also be controlled from the front panel or supplied remote.
When unmuted, the CH-Amp progressively restores the previous listening level rather than instantly applying full output.
Rechargeable Remote Control
A remote control is supplied with the CH-Amp.
It provides control over:
- Power
- Mute
- Input selection
- Volume
Additional buttons are provided for controlling a compatible EarMen Tradutto DAC.
The remote contains an internal rechargeable battery and is charged through USB-C.
PSU-3 Linear Power Supply Included
The CH-Amp is supplied with the separate EarMen PSU-3 rather than a conventional plug-top power adaptor.
Moving the mains transformer and associated high-voltage circuitry into a separate chassis helps keep potential electrical and magnetic noise away from the sensitive headphone-amplifier circuitry.
The PSU-3 also incorporates protection against:
- Current overload
- Short circuit
- Thermal overload
A Genuine Two-Box Headphone Amplifier
The separate power supply is a significant part of the CH-Amp rather than an optional upgrade.
The main amplifier weighs approximately 550g, while the PSU-3 weighs around 1.59kg.
That difference illustrates where much of the transformer and power-supply hardware is located.
PSU-3 Multi-Product Power Capability
The PSU-3 has been designed to supply more than the CH-Amp alone.
Alongside its dedicated ±12V supply for the headphone amplifier, additional 12V outputs can be used with compatible EarMen desktop components.
This means a matching EarMen system can use one PSU-3 to supply the CH-Amp together with products such as the Tradutto DAC and Staccato streamer.
Building an EarMen Desktop Stack
A complete EarMen system can combine the EarMen Staccato streamer, EarMen Tradutto DAC and CH-Amp.
The Staccato handles network streaming, Tradutto performs digital-to-analogue conversion and the CH-Amp provides headphone amplification, source selection and pre-amplifier control.
The supplied PSU-3 can provide the compatible power connections required by the stack, reducing the number of separate external power adaptors.
CH-Amp and EarMen Tradutto
The Tradutto is a particularly natural partner because it provides the digital-to-analogue conversion that the original CH-Amp deliberately omits.
A balanced 4.4mm connection can link the two products, maintaining balanced operation into the CH-Amp.
The CH-Amp remote also contains dedicated controls for compatible Tradutto operation.
CH-Amp and EarMen Staccato
The Staccato adds network streaming to an EarMen desktop system.
Because the CH-Amp itself has no digital or network functionality, a separate streamer and DAC are required before a Staccato network signal can reach the amplifier in analogue form.
The combination provides a modular system where streaming, conversion and amplification remain separately upgradeable.
CH-Amp or ST-Amp?
Choose the CH-Amp When
- You already own a suitable DAC
- Maximum headphone output is important
- Up to 3.8W balanced is useful
- A separate linear power supply appeals
- Remote control is important
- Multiple analogue inputs are useful
- You want the modular EarMen desktop stack
Choose the ST-Amp When
- You want an integrated USB DAC
- One compact chassis is preferable
- Up to approximately 1.85W is sufficient
- USB computer audio is required
- You want fewer separate components
- A lower overall system cost is important
The EarMen ST-Amp combines headphone amplification, pre-amplifier functionality and an integrated DAC in a single chassis.
CH-Amp or Angel?
Choose the CH-Amp When
- The system will primarily remain at home
- Greater headphone power is wanted
- Multiple analogue sources need connecting
- A 6.35mm headphone socket is preferred
- Remote control is useful
- A dedicated linear power supply appeals
- Analogue pre-amplifier duties are important
Choose the Angel When
- Portable operation is important
- An internal DAC is required
- USB digital audio is required
- S/PDIF digital inputs are useful
- Battery operation is required
- PCM and DSD file playback capability is important
The EarMen Angel is the more suitable choice where a portable DAC and headphone amplifier are required in one unit.
CH-Amp or a Headphone Output on an Integrated Amplifier?
Many integrated amplifiers include a headphone socket, but the circuitry behind it varies considerably.
A dedicated headphone amplifier such as the CH-Amp may be worthwhile where:
- The existing headphone output lacks sufficient power
- Balanced headphone operation is required
- Low and high gain are useful
- The headphones are particularly revealing
- Headphone listening forms a major part of the system
- A separate desktop listening position is wanted
The most useful comparison is always with the actual headphones and source that will be used.
System Matching
Well Suited To
- Full-size wired Hi-Fi headphones
- Balanced 4.4mm headphones
- Planar magnetic headphones
- Higher-impedance dynamic headphones
- External DACs
- CD players with analogue outputs
- Network streamers
- Phono stages
- Active loudspeakers
- Stereo power amplifiers
- Desktop listening systems
- EarMen Tradutto and Staccato systems
Check Before Buying
- No internal DAC
- No USB audio input
- No optical or coaxial digital inputs
- No Bluetooth
- No Wi-Fi or network streaming
- A separate DAC is required for digital sources
- Balanced headphones require a suitable 4.4mm cable
- High gain may be excessive for very sensitive earphones
- The supplied PSU-3 requires additional rack or desktop space
- Balanced pre-output can reach 8V
- This is the original CH-Amp rather than CH-Amp Signature
Placement and Ventilation
Both the CH-Amp and PSU-3 should be placed on a stable, level surface with reasonable airflow around the chassis.
Keep the power supply away from moisture and external heat sources and ensure the mains inlet remains accessible.
Do not cover either unit during operation.
Connection Guidance
- Reduce the CH-Amp volume before connecting headphones.
- Begin with low gain and move to high gain only where additional output is required.
- Use the 6.35mm connection for conventional single-ended headphones.
- Use a correctly wired 4.4mm cable for balanced headphones.
- Do not short balanced headphone outputs together through an unsuitable adaptor.
- Connect conventional analogue sources to Line 1 or Line 2 RCA.
- Use the 4.4mm input with compatible balanced sources.
- A turntable requires an external phono stage.
- Reduce the volume before connecting active speakers or a power amplifier.
- Confirm the receiving amplifier's input sensitivity before using high pre-amplifier levels.
- Set the PSU-3 mains-voltage selector correctly for the local supply.
- Use only compatible EarMen equipment with the additional PSU-3 DC outputs.
Key Features
- Desktop headphone amplifier
- Analogue pre-amplifier
- Fully balanced architecture
- Composite amplifier topology
- SoundPlus OPA1642 operational amplifiers
- WIMA capacitors
- Audio-grade electrolytic capacitors
- MELF low-noise resistors
- Two RCA single-ended inputs
- 2V RCA input sensitivity
- One balanced 4.4mm analogue input
- 4V balanced input sensitivity
- 6.35mm headphone output
- 4.4mm balanced headphone output
- Less than 1-ohm headphone output impedance
- Low gain
- High gain
- 2.9V low-gain single-ended output
- 260mW into 32 ohms single-ended in low gain
- 5.5V low-gain balanced output
- 1W into 32 ohms balanced in low gain
- 7V high-gain single-ended output
- 1.5W into 32 ohms single-ended in high gain
- 11V high-gain balanced output
- 3.8W into 32 ohms balanced in high gain
- THD+N as low as 0.0005%
- Signal-to-noise ratio greater than 116dB single-ended
- Signal-to-noise ratio greater than 118dB balanced
- Frequency response within ±0.005dB
- Single-ended RCA pre-output
- Balanced 4.4mm pre-output
- 4V single-ended pre-output
- 8V balanced pre-output
- 100-ohm RCA pre-output impedance
- 200-ohm balanced pre-output impedance
- Automatic headphone and pre-output operation
- OLED display
- Input-memory function
- Front input selection
- Front gain selection
- Volume control
- Push-to-mute volume control
- Remote control supplied
- USB-C rechargeable remote
- Tradutto remote-control functions
- Separate PSU-3 linear power supply
- PSU-3 overload protection
- PSU-3 short-circuit protection
- PSU-3 thermal protection
- Additional PSU-3 outputs for compatible EarMen products
- Aluminium main chassis
- Compact 150mm-square footprint
- Two-year manufacturer warranty subject to EarMen terms
Frequently Asked Questions
What is the EarMen CH-Amp?
It is a fully balanced analogue desktop headphone amplifier and pre-amplifier supplied with a separate PSU-3 linear power supply.
Does the CH-Amp contain a DAC?
No. The original CH-Amp is an analogue amplifier and requires a separate DAC for USB, optical, coaxial or other digital sources.
Is this the CH-Amp Signature?
No. This is the original CH-Amp. The later CH-Amp Signature is a different product with additional digital functionality.
Does it have USB audio?
No.
Does it have Bluetooth?
No.
Does it have Wi-Fi or streaming?
No. A separate streamer is required.
Is the CH-Amp fully balanced?
Yes. Balanced input signals remain balanced through the amplifier, while EarMen also converts single-ended input signals to balanced operation internally.
How many analogue inputs are there?
Three: two stereo RCA inputs and one balanced 4.4mm input.
What is the RCA input sensitivity?
EarMen specifies 2V.
What is the balanced input sensitivity?
EarMen specifies 4V.
Does it have a 6.35mm headphone socket?
Yes.
Does it have balanced headphone output?
Yes. A 4.4mm balanced headphone connection is provided.
How powerful is the single-ended headphone output?
In high gain, EarMen specifies up to 7Vrms and 1.5W into 32 ohms.
How powerful is the balanced headphone output?
In high gain, EarMen specifies up to 11Vrms and 3.8W into 32 ohms.
What does low gain provide?
Approximately 2.9V and 260mW into 32 ohms single-ended, or 5.5V and 1W into 32 ohms balanced.
What is the headphone output impedance?
Both headphone outputs are specified below one ohm.
Can it drive planar magnetic headphones?
Its maximum 3.8W balanced output makes it suitable for many planar magnetic headphones, although suitability still depends on sensitivity, impedance and required listening level.
Can it drive high-impedance headphones?
The maximum 7Vrms single-ended and 11Vrms balanced output provides considerable voltage capability for many high-impedance headphones.
Can I use sensitive IEMs?
Potentially, although low gain should be used first. Very sensitive earphones are worth demonstrating because required volume range and perceived noise floor vary considerably.
Does it work as a pre-amplifier?
Yes. Both single-ended RCA and balanced 4.4mm variable pre-amplifier outputs are provided.
Can I connect active speakers?
Yes, provided they have suitable analogue inputs.
Can I connect a power amplifier?
Yes. Reduce the CH-Amp's volume first and confirm that the power amplifier's input sensitivity and maximum input level are suitable.
What is the RCA pre-output level?
EarMen specifies up to 4V with an output impedance of 100 ohms.
What is the balanced pre-output level?
EarMen specifies up to 8V with an output impedance of 200 ohms.
Can headphones and the pre-outs play simultaneously?
The CH-Amp changes automatically between headphone and pre-amplifier operation. With headphones disconnected, Pre mode is active. Connecting headphones activates headphone output.
Does it have an OLED display?
Yes. It displays information including input, volume, gain and pre-amplifier operation.
Does it remember the selected input?
Yes. The previously selected input is retained after the unit is switched off.
Does it include a remote control?
Yes.
Is the remote rechargeable?
Yes. The remote is charged through USB-C.
Can the remote control the Tradutto?
Yes. Dedicated Tradutto controls are included on the CH-Amp remote.
Is the PSU-3 included?
Yes. The separate linear PSU-3 is supplied as part of the CH-Amp package.
What is the purpose of the separate PSU-3?
It keeps the mains transformer and much of the power-supply circuitry outside the headphone-amplifier chassis while providing low-noise DC power to the CH-Amp.
Can the PSU-3 power anything else?
Yes. Additional 12V outputs are provided for compatible EarMen desktop equipment such as the Tradutto DAC and Staccato streamer.
Can I connect a turntable?
Yes, but only through a suitable external phono stage. The CH-Amp does not contain a phono input.
Can I connect a CD player?
Yes, provided the player has a conventional analogue output or is connected through a separate DAC.
Can I connect a network streamer?
Yes, if the streamer provides an analogue output. A digital-only streamer requires a separate DAC.
What are the CH-Amp dimensions?
Approximately 150 x 30 x 150mm.
How much does the CH-Amp weigh?
Approximately 550g.
What are the PSU-3 dimensions?
Approximately 150 x 60 x 150mm.
How much does the PSU-3 weigh?
Approximately 1.59kg.
What is the warranty?
EarMen provides a two-year limited manufacturer warranty against defects in materials and workmanship, subject to registration and the company's current warranty conditions.
Related EarMen Products and Audio T Guides
Why Buy From Audio T?
- EarMen CH-Amp demonstrations
- Headphone matching advice
- Balanced and single-ended comparisons
- Low and high gain setup guidance
- Planar magnetic headphone matching
- High-impedance headphone matching
- External DAC selection
- Tradutto and Staccato system demonstrations
- Active-speaker integration advice
- Power-amplifier integration guidance
- Balanced 4.4mm cable advice
- Comparison with alternative desktop headphone amplifiers
- Ongoing setup and after-sales support
Contact your local Audio T store to arrange a demonstration or discuss matching the EarMen CH-Amp with your headphones, DAC, active speakers or existing Hi-Fi system.