Benchmark HPA4 Headphone / Line Amplifier
Benchmark HPA4’s THX-888 architecture delivers a jet-black background, explosive dynamics and remarkably precise imaging. HiFi News admired its openness, impact and atmosphere, while The Ear highlighted its vast, finely layered soundstage. With serious drive, relay-controlled volume precision and full preamp flexibility, this is uncompromisingly revealing reference amplification.
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Deliciously Crispy
Sound Quality
96/100
Build Quality
91/100
Features Usability
90/100
Value for Money
85/100
Pros
Exceptionally transparent, low-noise presentation reveals fine detail without adding obvious coloration.
Delivers expansive, stable imaging and convincing depth for both headphone and line-stage use.
High-current, high-voltage output drives a wide range of low- and high-impedance headphones with authority.
Versatile analogue hub with balanced and single-ended headphone connections, multiple inputs, preamp outputs and precise relay volume control.
Cons
Its unforgiving neutrality can expose weak recordings and mismatched upstream or downstream components; some listeners may find it dry or less tonally rich.
Premium pricing and the lack of an integrated DAC make it a more involved, costly system proposition.
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What Reviewers Are Saying
SOUND QUALITY PERFORMANCE 96/100
Reviewers describe an exceptionally transparent, quiet and controlled amplifier that combines forensic detail with expansive, stable imaging and unusually effortless drive. Its uncompromising neutrality can expose lean or dry-sounding recordings, so listeners seeking added warmth or tonal density may prefer a more characterful alternative.
Transparency Resolution
97/100
The Ear calls its resolution truly remarkable, while Soundnews says it reveals the source and nothing more. HiFi News similarly praises its openness and ability to pass through performers', producers' and engineers' intent, with The Absolute Sound finding it super-revealing.
Tonal Balance Musicality
93/100
Reviews consistently hear a neutral, uncoloured presentation rather than an overtly warm or romantic one. HiFi News finds it vivid, atmospheric and sincere, and Hans Beekhuyzen praises natural voices and silky highs, though The Ear and The Absolute Sound note that some material can sound less rich or dry.
Dynamics
96/100
Soundnews reports lightning-quick control and thunderous slam, including substantial remaining headroom with demanding headphones. HiFi News says it can reach very high levels without changing character, while The Absolute Sound hears a layered, dynamic yet relaxed presentation.
Noise Floor
96/100
Soundnews describes the background as the blackest and cleanest it has encountered, and Hans Beekhuyzen calls it blacker than black. The Ear likewise attributes its unusually pure presentation to an ultra-low noise floor, with no reviewer reporting audible hiss or hum.
Headphone Compatibility
96/100
The Ear found low- and high-impedance headphones equally easy to drive, while The Absolute Sound highlights the combination of high voltage, high current and near-zero output impedance for low-sensitivity and varied-impedance loads. Soundnews also reports authoritative control with planar-magnetic headphones from the balanced output.
Assessments of Build Quality, Usability, and Overall Propositions.
Build Quality
91/100
Soundnews calls the construction impeccable, citing the thick metal enclosure and substantial aluminium front panel. The reviews also describe a functional, sober design and carefully implemented relay-controlled control system, though there is limited discussion of long-term durability.
Features Usability
90/100
This is a well-equipped analogue amplifier and preamp, with balanced and single-ended headphone connections, multiple RCA and XLR inputs, balanced and RCA preamp outputs, and 12V triggers. HiFi News praises the touchscreen's input naming and level-management options, while the 256-step relay volume system supports precise everyday control; it does not include a DAC.
Value for Money
85/100
At roughly $3,000-$3,800 depending on market, this is an expensive all-analogue amplifier, and Soundnews identifies price as its principal drawback. However, Hans Beekhuyzen considers it worth every cent, while Alpha Audio cautions that the audible gains may be subtle for many listeners.
Reviews & Sources
Professional reviews and sources for this product's Watt'n Potatoes analysis.
Online Reviews & Mentions
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Specifications
- THX-888 Headphone Output
- THD < -125 dB (0.00006%) SNR > 131 dB, unweighted, 20-20 kHz SNR > 135 dB, A-weighted Frequency Response - 0.003 dB at 10 Hz, -0.001 dB at 20 kHz - 3 dB Bandwidth exceeds 0.1 Hz to 500 kHz Output Impedance, near 0 Ohms Output Noise < 2.45 uV at Unity Gain, 20-20 kHz Maximum Output Power, 6 Watts into 16 Ohms Maximum Output Current, 1.5 A Maximum Output Voltage, 11.5 Vrms into 300 Ohms Crosstalk < -133 dB @ 1 kHz, -115 dB @ 10 kHz (XLR4)
- Balanced Line Outputs
- THD < -125 dB (0.00006%) SNR > 135 dB, unweighted, 20-20 kHz SNR > 137 dB, A-weighted Frequency Response - 0.003 dB at 10 Hz, -0.001 dB at 20 kHz - 3 dB Bandwidth exceeds 0.1 Hz to 500 kHz Output Impedance 60 Ohms Output Noise < 1.9 uV at Unity Gain, 20-20 kHz Maximum Input and Output Voltage, 20 Vrms (+28 dBu) Crosstalk < -133 dB @ 1 kHz, -116 dB @ 10 kHz
- Dimensions
- 8.65" W x 3.88" H x 8.33" D - Including Feet 8.65" W x 3.47" H x 8.33" D - Excluding Feet
- Weight
- 8.0 lbs., 12 lbs. shipping
- Power
- 18W Typical Input Power 35W Maximum Input power 0.33 W Standby Power (when off) Internal Universal Power Supply
Manufacturer's Description — Benchmark
The HPA4 features the Benchmark-exclusive THX-888 headphone amplifier. This is Benchmark's flagship headphone amplifier. It also marks the pinnacle of the THX headphone amplifier family. The THX-888 circuit board is manufactured by Benchmark.
Like our AHB2 power amplifier, the THX-888 features the patented THX-AAA feed-forward topology. The THX-888 keeps noise and distortion below the threshold of hearing, even when driving the most difficult headphones.
The award-winning HPA4 packs power, speed, and control into a package that includes all of the functions and features of our LA4 line-level preamplifier.
The headphone and line outputs are controlled by independent 256-step relay-switched attenuators. This is, without question, the best analog volume control system available.
- Much Faster than Feedback
- Eliminates Zero-Crossing Distortion
- Inherently Stable, Non-Recursive Correction
- Stable into Any Phase Angle
- Stable when Driving Very Low impedances
- No Rise in THD when Driving Low Impedance Headphones
- Flagship THX-888 Headphone Amplifier
- 30 to 40 dB reduction in THD
- Keeps THD+N Below 0 dB SPL at All Times
- No "Electronic Fingerprints" on the Music
- Accurate Impulse Response Into all Loads
- 135 dB SNR
- Ultra Wide 0.1 Hz to 500 kHz Response
- Bass is Delivered Without a Phase Shift
- Fast, Distortion-Free Transient Response
- Linear Phase Response
- Accurately Reproduces the Audio Waveshape
- Precise Rendering of Stereo Width and Depth
- Focused 3-D Stereo Image
- High Output Current - Drives Low Impedances with Ease
- High Output Voltage - Ample Headroom to Dive Inefficient Headphones
- 0-Ohm Output Impedance - Maintains Tight Control of Drivers
- Fault-Detection Circuit- Protected against Short Circuits and Overloads
- Dual Outputs - XLR4 and 1/4" TRS
- Independent Line and Headphone Balance Controls
- High-Precision Low-Impedance 256-Step Attenuator
- Low-Noise 16-Step Input Gain Stage
- Control Range is +15 dB to -127.5 dB in 0.5 dB Steps
- High Precision Laser-Trimmed Thin-Film Resistors
- 12 Relays per Output - 48 Total Including Line Outputs
- Precision Make-Before-Break Timing - Prevents Switching Noise
- The HPA4 Includes all LA4 Features
- 2 Pairs of Balanced Line Inputs
- Fully-Balanced Differential Input Amplifiers
- Fully-Balanced Relay-Controlled Gain Stage
- Fully-Balanced Relay-Controlled Attenuation Stage
- Fully-Balanced Output Line Drivers
- Left, Right and Mono - Balanced Line Outputs
According to independent tests, the Benchmark HPA4 delivers the lowest noise and lowest distortion available from a headphone amplifier or from a preamplifier.
The Benchmark-excusive THX-888 headphone amplifier board features the patented THX-AAA technology. This technology includes a feed-forward error correction system that reduces distortion by 30 to 40 dB. Distortion and noise are held below the 0-dB SPL threshold of hearing, even when driving the most demanding headphones.
The amplifier board is driven by a 256-step relay-controlled volume control. This system is engineered to deliver the lowest possible noise and distortion at each volume setting. A second, identical and fully-independent volume control drives the balanced and unbalanced line outputs.
The HPA4 has won many top awards and top recommendations from the press. It has received two "Product of the Year" awards, and is currently listed on Stereophile's short list of recommended components.
The Benchmark HPA4 delivers a clear, open, and uncluttered playback across the entire frequency range.
Instrumental overtones are rendered with exceptional precision and realism. Vocals are reproduced with outstanding accuracy and natural tones. Transients are fast and precise. Bass is deep and well controlled.
The ultra-linear phase response of the HPA4, allows it to create a precise three-dimensional rendering of the recorded space. This space is open and uncluttered because noise and distortion are held below the 0-dB SPL threshold of hearing at all playback levels.
This experience is not limited to the headphone outputs. The HPA4 includes all of the features and functions of the LA4 preamplifier, and this is perfect match for driving Benchmark's AHB2 power amplifier.
Headphone and line output volume are independently controlled.
- On/Off Momentary Switch
- IR Remote Sensor
- Color Touch-Screen Display
- Attenuation Shown in dB
- Many Programmable Features
- 1/4" TRS Jack - Professional Grade Connector
- XLR4 Jack - Provides the Best Output Connection
- Long-Life Heavy-Duty Optical Encoder
- 0.5 dB per Step, 256 Steps
- Push to Toggle Between Line and Headphone
- Allows Independent or Simultaneous Control of Line and Headphones
- Input 1 - XLR (L,R)
- Input 2 - XLR (L,R)
- Input 3 - RCA (L,R)
- Input 4 - RCA (L,R)
- Left Out - XLR
- Right Out - XLR
- Mono Sum Out - XLR
- Left Out - RCA
- Right Out - RCA
- Bidirectional Operation
- Work with all Single and Dual Direction Trigger Ports
- Time Delays Allow Noise-Free System Startup and Shutdown
- Standard 3-Pin IEC Connector
- Fuse Drawer with Two Fuses
- Auto-Ranging
- 50-60 Hz
Verified Dealers
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Authorized dealers for Benchmark HPA4 Headphone / Line Amplifier
- The Music Room — online and in-store — Erie, Colorado, United States (website)
- 110Hz — online and in-store — Kielce, Województwo świętokrzyskie, Poland (website)
- Acton Gate Audio — online and in-store — Cymru, United Kingdom (website)
- Alto Music — online and in-store — Middletown, New York, United States (website)
- Atlas Pro Audio, Inc. — online and in-store — Sun City Center, Florida, United States (website)
- Audio Advisor — online and in-store — Michigan, United States (website)
- Audio Extreme — in-store — Kowloon, China (website)
- Audiolab Stereo & Video — online and in-store — Morrisville, Pennsylvania, United States (website)
- AUDIOPHONICS — in-store — Bordeaux, Nouvelle-Aquitaine, France (website)
- B&H Photo — online and in-store — New York, New York, United States (website)
and 23 more verified dealers