Benchmark HPA4 Headphone and Line Amplifier

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Benchmark HPA4 Headphone and Line Amplifier

Hailed as the world’s Ultimate Line Amplifier, HPA4 is the product of a collaboration between Benchmark Media Systems and THX Ltd. It is the first headphone and line amplifier to feature THX’s Achromatic Audio Amplification technology (or AAA) and reduces harmonic/intermodulation/crossover distortion by up to 40dB. The reduction is achieved by utilising a patented feed-forward topology which nullifies conventional distortion and noise mechanisms.

With HPA4, Benchmark and THX have produced a headphone and line amplifier capable of technically reaching maximum output and SPL without the usual side effect of distortion, delivering power, audio fidelity, speed and accuracy onto a silent canvas.

Benchmark HPA4 Headphone and Line Amplifier

More Information
Manufacturer Link Benchmark HPA4 Headphone and Line Amplifier
Manufacturer Benchmark
Free warranty 3 years
Delivery Charge Free
Delivery Time Normally 1 - 5 Working Days (Covid-19 and Brexit Delays Possible, contact us for more information)
Card Surcharge No
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Benchmark HPA4 Headphone and Line Amplifier

Main 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
  • DC Protection
  • Over-Voltage and Over-Current Protection
  • Thermal Protection
  • Touch Screen Control
  • IR Remote Control (optional)
  • 2 Balanced Stereo Line Inputs
  • 2 Unbalanced Stereo Line Inputs
  • 1 Balanced Stereo Line Output
  • 1 Unbalanced Stereo Line Output
  • 1 Balanced Mono Sum Output
  • 2 Bidirectional 12V Trigger Ports


< -125 dB (0.00006%)
135 dB, unweighted, 20-20 kHz (> 131 dB THX)
SNR (A-Weighted):
137 dB (> 135 dB THX)
Frequency Response:
-0.003 dB at 10 Hz, -0.001 dB at 20 kHz
60 Ohms (near 0 Ohms THX)
Output Noise:
< 1.9 uV at Unity Gain, 20-20 kHz (< 2.45 uV THX)
Maximum Input:
20 Vrms (+28 dBu)
Maximum Output:
20 Vrms (+28 dBu)
< -133 dB @ 1 kHz, -116 dB @ 10 kHz


Power Supply:
Typical Input Power:
Max Input Power:
Standby Power:
0.33W (when off)

Physical Properties

WxHxD 8.65 x 3.88 x 8.33" (Including Feet)
8.0 lbs (12 lbs shipped)

Benchmark HPA4 Headphone and Line Amplifier