User manual
Benchmark HPA4 Reference Headphone Line Amplifier

User Manual for Benchmark HPA4 Reference Headphone Line Amplifier with Remote Control

• Product category: Headphone Amplifiers Benchmark
• Brand: Benchmark
• Description and content of package
• Technical information and basic settings
• Frequently asked questions – FAQ
• Troubleshooting (does not switch on, does not respond, error message, what do I do if...)
• Authorized service for Benchmark Headphone Amplifiers

Product description

THX AAA Technology
• The collaboration between Benchmark and THX features THX Achromatic Audio Amplifier (AAA) technology, which reduces harmonic, intermodulation, and crossover distortion by 20 to 40 dB to guarantee a realistic and fatigue-free listening experience. It accomplishes this using a patented feed-forward topology to null conventional distortion and noise mechanisms, resulting in extreme linearity. THX AAA allows the amplifier to reach its maximum output power and sound pressure level without producing the distortion that normally accompanies increased output levels in traditional amplifiers.

Line Amplification
• The THX-888 amplifier is driven by a Benchmark line amplifier that features relay gain control, relay input selection, and relay muting. The line amplifier incorporates premium gold-contact relays. The gain control has 256 steps in 0.5 dB increments. It also features a balance control. Relay closures are precisely timed to deliver smooth volume changes. The HPA4 includes four independent 256-step attenuators: two for the headphone outputs and two for the line outputs. To make this all happen, the HPA4 includes a total of 64 precision relays.

100% Analog Signal Path
• The HPA4 is 100% analog and should be driven from an external D/A converter or analog source. It eclipses the performance of typical high-end preamplifiers by achieving much lower noise and distortion.

High Voltage, High Current, and High Power
• The THX-888 amplifier can cleanly deliver high voltage into low-sensitivity, high-impedance headphones and it can cleanly deliver high power and current into low-impedance headphones. The HPA4 delivers 11.9 Vrms into 300 Ohms and 6W into 16 Ohms. Given these extreme capabilities, Benchmark has incorporated several protection systems to protect expensive headphones and the amplifier itself. These include DC, short-circuit, over-current, over-voltage, and thermal protection.

Speed and Precision
• The bandwidth of the HPA4 extends from 0.01 Hz to over 500 kHz with a drop of only 3 dB. The 10 Hz to 20 kHz spectrum boasts a maximum variance of only -0.003 dB. This means that the HPA4 delivers very precise amplitude and phase accuracy over the entire audio bandwidth. Wave shapes are accurately reproduced, and the entire spectrum is delivered with precise timing.

Balanced and Unbalanced I/O
• The headphone output of the THX-888 amplifier features a 1/4" TRS and an XLR 4-pin. While both outputs deliver the full performance of the HPA4, the XLR4 is most ideal due to its lower contact resistance. The HPA4 features two balanced stereo inputs via XLR 3-pin jacks and two unbalanced stereo inputs via RCA jacks. The line amplifier provides one balanced stereo output, one balanced mono sum, and one unbalanced stereo output.

Touchscreen
• The touchscreen provides easy access to advanced features such as balance control, input level offsets, input names, screen dimming, remote control, and function locking. Help screens explain the special functions.

Rotary Encoder
• The volume control knob features a high-quality optical encoder that is rated for heavy use. An acceleration feature makes it easy to move through the 256 volume steps while maintaining 0.5 dB/step resolution. A press of the control knob toggles between headphone volume, line out volume, or both.

Trigger Ports
• Two bidirectional 12V trigger ports can be used to link the HPA4 with external D/A converters and power amplifiers. The trigger signal controls the power-up and power-down sequencing of the entire audio system. The trigger ports are compatible with most industry-standard trigger input or output ports, but can communicate bidirectionally with other Benchmark products.

Convenience Features
• The HPA4 includes independent on-screen mute buttons for the headphone and line outputs. Both can also be muted with the volume knob or with the supplied remote control. An on-screen -20 dB dim button instantly reduces the level by 20 dB, providing a temporary volume reduction and an easy return to the previous listening level. This control makes it easy to transition between a normal listening level and a background level. The dim function is also accessible from the remote control. Inputs may be renamed and unused inputs may be disabled. Input levels can be trimmed to provide input-to-input level matching. Screen brightness is adjustable and timers can be set to dim or shut off the display. The screen can be locked to prevent access to advanced features.

Sleek and Sturdy Construction
• The case features a milled faceplate and milled sides. Top, bottom, and rear panels are made from thick aluminum and feature a brushed texture. The HPA4 was designed, assembled, and tested in the USA.

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Technical parameters

Benchmark HPA4 Specs

Number of Channels	2
Input Connections	4 x 3-Pin XLR Female (Two Stereo Pairs, Balanced) 4 x RCA Coaxial (Two Stereo Pairs, Unbalanced)
Output Connectors	2 x 3-Pin XLR Male (One Stereo Pair, Balanced) 1 x 3-Pin XLR Male (Mono, Balanced) 2 x RCA Coaxial (One Stereo Pair, Unbalanced) 1 x 4-Pin XLR Headphone Jack (Balanced) 1 x 1/4" TRS Headphone Jack (Unbalanced)
Trigger Connectivity	2 x 12 V Bidirectional Trigger Ports
Maximum Input Level	20 Vrms / +28 dBu
Maximum Output Level	Line Outputs: 20 Vrms / +28 dBu Headphone Output: 11.5 Vrms into 300 Ohms
Maximum Output Power	Headphone Output: 6 W into 16 Ohms
Output Impedance	Line Outputs: 60 Ohms Headphone Output: Near 0 Ohms
Function Controls	Volume Power
Frequency Response	Exceeds 0.1 Hz to 500 kHz (-3 dB) 10 Hz (-0.003 dB) to 20 kHz (-0.001 dB)
THD + N	< -125 dB (0.00006%)
Output Noise	Line Outputs: <1.9 Rating 100% users recommend this product to others. And what about you? This product has already been rated by 75 owners. Add your rating and experience with the product. Discussion Ask our technicians if you have a problem with your settings, or if anything is unclear in the user manual you have downloaded. You can make use of our moderated discussion. The discussion is public and helps other users of our website who may be encountering similar problems. The discussion is empty - enter the first post Post a new topic / query / comment: Items marked with * are required. Your name *: E-mail : Subject *: Message *: Your email address will not be displayed. Do not forget to fill it in if you want to receive a reply to your enquiry/contribution. Processing of personal data in accordance with GDPR