John Siau Tears Down a Benchmark HPA4 Headphone/Line Amplifier

Lots of Relays and a Very Special Headphone Amplifier

Benchmark's lead engineer, John Siau, shows us what is hidden inside Benchmark's flagship HPA4 and LA4 preamplifiers. The HPA4 preamplifier includes the Benchmark-designed THX-888 headphone amplifier board.

We will find precision relays, custom high-precision resistors, feed-forward error correction circuits, and much more.

Discover the hidden secrets of the LA4 and HPA4 Preamplifiers.

This is John's second teardown video. Last month he tore down an AHB2. A DAC3 teardown will be featured soon.

Are You Driving Your Audio System in the Wrong Gear?

Match Your Audio Levels ... Drive in the Right Gear!

A race car produces peak power when the transmission is in the proper gear. Likewise, an audio system produces peak performance when each component is running at an optimum signal level.

Volume controls and gain switches are the "gearboxes" in an audio system. Learn how to "drive in the right gear". 

"The LA4 is the equivalent of an automatic transmission for your audio system."

Learn how an LA4 can boost system performance by matching the output of your DAC to the input of your power amplifier.

Building a Better Volume Control

An Impossible Engineering Task?

We wanted to be able to place an analog volume control in front of our AHB2 power amplifier or in front of our THX-888 headphone amplifier without diminishing the performance of either device. Our volume control would need to have lower distortion and lower noise than either of these amplifiers. No existing analog preamplifier technology was up to the task!

Furthermore, we wanted to meet or exceed the limits of human hearing: The LA4 volume control range matches the 130 dB dynamic range of human hearing. The 0.5 dB step size is one half of a "just noticeable difference" in volume. And, in a typical system, the distortion and noise are held well below the 0 dB SPL threshold of human hearing.

We achieved this using a set of fully-buffered, fully-balanced, low-impedance, relay-controlled attenuators. This concept was not new, but we pushed the technology far beyond that of previous examples.

No other analog preamplifier matches the performance, precision, or range of the LA4 and HPA4 relay-controlled preamplifiers.

Not Just a "Good Preamplifier"

"Benchmark's LA4 is the widest-bandwidth, widest-dynamic-range, lowest-noise, lowest-distortion preamplifier I have encountered. 

- John Atkinson, Stereophile Magazine

Watch as Benchmark's lead Engineer, John Siau, takes us on a deep dive into the relay-controlled preamplifiers inside Benchmark's LA4 and HPA4.

Benchmark Media Systems

203 East Hampton place, STE 2, Syracuse, New York 13206, United States

[email protected]

benchmarkmedia.com

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