Benchmark HPA4 High Resolution Headphone and Line Amplifier
£3,499

Features
- THX-888 (AAA™) Headphone Amplifier
- Benchmark Line Amplifier
- 256-Step Fully-Balanced Relay Gain Control, 0.5 dB Steps
- Precision Timed Relay Closures
- Precision Metal Film Resistors
- Gold-Contact Relays
- Balanced and Unbalanced I/O
- 6 Watts into 16 Ohm Headphones
- 11.5 Vrms into 300 Ohm Headphones
- Short-Circuit Protection

Specifications
THX-888 Headphone Outputs | Test conditions: 1 kHz test tone, Output Level = +21 dBu, Unity Gain (unless noted) |
Number of Headphone Outputs | 2 |
Output Connector – Differential Drive | Gold-Pin Neutrik™ XLR4 – female |
Output Connector – Common Ground Return | 1/4″ Neutrik™ TRS Jack |
SNR | 135 dB, A-Weighted 131 dB, 20 Hz to 20 kHz |
Output Noise | < 2.45 uV, 20 Hz to 20 kHz |
Frequency Response | -0.006 dB at 10 Hz -0.014 dB at 20 kHz -3 dB at 0.1 Hz and 500 kHz |
Output Impedance | Near 0 Ohms |
Maximum Output Power and Voltage | 6 Watts into 16 Ohms, 9.8 Vrms 2.6 Watts into 45 Ohms, 10.8 Vrms 640 mW into 200 Ohms, 11.3 Vrms 440 mW into 300 Ohms, 11.5 Vrms |
Maximum Output Current (protection threshold) | 1.5 Amps |
Crosstalk, XLR4 Output | -133 dB@1kHz, -115 dB@10kHz |
THD, 16-Ohm Load | -125 dB, 0.00006%, 16-Ohm Load |
THD+N, 20 kHz BW, 16-Ohm load | -115 dB, 0.00018% |
Volume Control Range | Mute, -112 dB to +15 dB in 0.5 dB steps |
Balance Control Range | +/- 6 dB in 0.5 dB steps |
Balanced Analog Outputs | Test conditions: 1 kHz test tone, Output Level = +24 dBu, Unity Gain (unless noted) |
Number of Balanced Analog Outputs | 3 (left, right, mono sum) |
Output Connectors | Gold-Pin Neutrik™ XLR – male |
SNR | 137 dB, A-Weighted 135 dB, 20 Hz to 20 kHz |
Output Noise | < 2.1 uV, 20 Hz to 20 kHz |
Frequency Response | -0.005 dB at 10 Hz -0.001 dB at 20 kHz -3 dB at 0.1 Hz and 500 kHz |
Output Impedance | 60 Ohms |
Maximum Output Level | +28 dBu, 19.5 Vrms |
THD | -126 dB, 0.00005% |
THD+N, 20 kHz BW | -115 dB, 0.00018% |
Volume Control Range (with 0 dBFS digital input) | Mute, -112 dB to +15 dB in 0.5 dB steps |
Balance Control Range | +/- 6 dB in 0.5 |
Unbalanced Analog Outputs | Test conditions: 1 kHz test tone, Input Level = 2 Vrms, Unity Gain (unless noted) |
Number of Unbalanced Analog Outputs | 2 (left, right) |
Output Connectors | Gold RCA – female |
SNR | 116 dB, A-Weighted 108 dB, 20 Hz to 20 kHz |
Output Noise | < 8 uV, 20 Hz to 20 kHz |
Frequency Response | -0.008 dB at 10 Hz -0.005 dB at 20 kHz -3 dB at 0.1 Hz and 500 kHz |
Output Impedance | 30 Ohms |
Maximum Output Level | +12.2 dBu, 3.2 Vrms |
Volume Control Range (with 0 dBFS digital input) | Mute, -112 dB to +15 dB in 0.5 dB steps |
Balance Control Range | +/- 6 dB in 0.5 dB steps |
Balanced Analog Inputs | |
Number of Unbalanced Analog Inputs | 4 (2 stereo pairs) |
Input Connectors | Gold-Pin Neutrik™ XLR – female |
Input Impedance | >50 k Ohms |
Maximum Input Level | +28 dBu, , 19.5 Vrms |
Input Selection and Muting | Gold-Contact Relays |
Input State when Power is Off | Inputs are Disconnected using Relays |
Unbalanced Analog Inputs | |
Number of Unbalanced Analog Inputs | 4 (2 stereo pairs) |
Input Connectors | Gold RCA – female |
Input Impedance | >50 k Ohms |
Maximum Input Level | +12.2 dBu, 3.2 Vrms |
Input Selection and Muting | Gold-Contact Relays |
Input State when Power is Off | Inputs are Disconnected using Relays |
AC Power Requirements | |
Nominal Operating Range | 100 – 240 VAC, 50 – 60 Hz |
Min/Max Operating range | 90 – 260 VAC, 47 – 63 Hz |
Power | < 0.5 Watts Standby 15 Watts Typical Program 28 Watts Maximum |
Fuses (2 required) | 5×20 mm, 0.5 A 250 V Slo-Blo® Type |
Dimensions | Form Factor ½ Rack Wide, 2 RU High Depth – excluding knob and connectors 8.33” (220 mm) Overall Depth – including knob and connectors 9.33” (237 mm) Width 8.65” (220 mm) Height – excluding feet 3.47″ (88 mm) Height – including feet 3.88” (99 mm) |
Weight | HPA4 only 8 lb. HPA4 with remote, power cord and manual 9 lb. |
Shipping weight | 12 lb. |

Description
THE ULTIMATE HEADPHONE AND LINE AMPLIFIER
The HPA4 is Benchmark’s newest headphone amplifier. Benchmark Media Systems, Inc. and THX, Ltd. have partnered to introduce the Benchmark HPA4 headphone/line amplifier featuring THX Achromatic Audio Amplifier (AAA™) technology.
THX AAA™ reduces harmonic, intermodulation, and crossover distortion by 20 to 40 dB to guarantee a realistic, fatigue-free listening experience. It accomplishes this using a patented feed-forward topology to null conventional distortion and noise mechanisms, resulting in the world’s most linear amplifier. THX AAA allows the amplifier to reach its maximum output power and sound pressure level (SPL) without producing the distortion that normally accompanies increased output levels in traditional amplifiers.
Featuring the flagship THX-888 amplifier design, the revolutionary HPA4 headphone amplifier incorporates the same THX AAA technology that Benchmark uses in the AHB2 power amplifier. The HPA4 delivers sonic perfection. Hear the music without any contamination from electronic noise or distortion. The HPA4 delivers power, audio fidelity, speed and accuracy over an utterly silent background.
The THX-888 amplifier is driven by a Benchmark line amplifier that features relay gain control, input selection, and muting. The line amplifier incorporates the finest gold-contact relays available. The gain control has 256 steps in 0.5 dB increments. It also features a balance control. Relay closures are precisely timed to deliver silky-smooth volume changes. No other relay gain control offers this level of precision and performance. The HPA4 includes 4 independent 256-step attenuators: two for the L&R headphone outputs, and two for the L&R line outputs. To make this all happen, the HPA4 includes 64 precision relays.

Additional information
Colour | Black, Silver |
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Delivery Info
Delivery Information
As a company our primary goal is to provide a seamless service that results in customer satisfaction. We aim to deliver within 3 working days. Unfortunately, there may be occasions where this time frame may not be met due to unforeseen circumstances; in this instance, we deliver product/s as soon as we can. All delivery charges are included within the prices quoted, unless otherwise specified.
All small items are usually delivered between 9am and 6pm, on a Monday to Friday, unless a Saturday delivery is requested. Follow My Parcel is an industry-changing innovation from DPD Local, which will give your customers unparalleled levels of information and peace of mind.Not only will your customers receive a one hour delivery timeslot, but they’ll now also be able to track the progress of their parcels on a map as our drivers make their way to the delivery addresses. Follow My Parcel will:
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