During the Covid 19 period we are operating the showrooms as appointment only - click here to book.

Benchmark HPA4 Headphone and Line Amplifier

In stock
See more Benchmark products.

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
See more Benchmark products.

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