Feed-Forward Error Correction

Don't look back, the future is here!

Benchmark's AHB2 power amplifier has a unique feedforward error correction system that cancels distortion before it reaches the speaker terminals. In contrast, global feedback systems attempt to correct the distortion after it reaches the speaker terminals.

Feed-forward correction is fast, precise, and inherently stable.

Benchmark's AHB2 blends feedback with feed-forward correction to leverage the best characteristics of each.

Listen to Gene and John as they discuss this revolutionary technology.

• How does the feed-forward system know what correction to send?
• Does it predict the future?
• What makes feedback unstable when driving capacitive loads?
• Why is feed-forward stable when driving capacitive loads?

Take a few minutes to learn how feed-forward error correction works:

• Watch as John provides an easy-to-understand analogy for feed-forward error correction.
• Join the discussion.
• We reserve the right to limit negative feedback.

The FFT … an Audio Microscope.

An FFT analyzer is like an audio microscope. It allows us to easily measure the frequency and amplitude of tones that are below the level of the noise. Traditional audio meters fail when the signal is lower than the noise level, but with an FFT, we can accurately measure tones that are 30 to 40 dB below the level of the noise.

In many ways, our ears behave like an FFT audio measurement system. Our ears can detect the frequency and amplitude of tones that are as much as 30 dB below the ambient noise. This means that our ears are 30 dB better than traditional audio meters! This is why we can carry on a conversation in a noisy room, and this is why we can hear individual instruments within an orchestra. This is also why small defects need to be detected and corrected when designing top-quality audio gear.

John Siau, Benchmark’s lead Engineer, will explain the “magic” of the FFT analyzer without the use of advanced mathematics. He will show an FFT analyzer in action, and he will measure a complete Benchmark chain to determine if it produces audible noise or distortion. Learn how to read an FFT plot and learn what to look for when selecting audio components.

Don't Become a Victim of "Wire Fraud"!

Beware of claims that sound too good to be true. Beware of pseudo-scientific language. Beware of any company, reviewer, or salesperson that describes the "sound" of an audio cable.

If the "sound" of a cable is described in words such as richness, detail, width, or texture, hang onto your wallet. Beware of any promise that a cable will provide a quick fix for your sound system.

While every cable has some measurable impact on the electrical signal flowing through it, this impact is normally well below the threshold of audibility. Of all of the components in an audio chain, cables contribute the smallest errors.

If you want to invest in great sound, cables will yield a very poor ROI.

In this video we will compare the magnitude of the errors contributed by the cables to those of the electronics, the loudspeakers, the listening room, and the music delivery medium. We will show that wires are orders of magnitude less important than these other system components.

Adopt a Sound Investment Strategy

Benchmark's lead engineer, John Siau, presents an "Audio Investment Strategy" that prioritizes investing in the components that yield the highest returns. Cables are at the very bottom of his priority list. Find out why!

Are You Driving Your Audio System in the "Wrong 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. We can put a race car on a dynamometer and measure the power that is delivered to the wheels. We can also measure the loss of power that comes from driving in the wrong gear.

Likewise, we can hook an audio system up to a test station and measure the power and noise that is delivered to our speakers. We can also measure the loss of performance that comes from operating the audio system in the "wrong gear".

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

John Siau will take us into Benchmark's Engineering Lab for a performance driving lesson. He will show end-to-end performance measurements of a high-performance Benchmark audio system. He will even "shift it into the wrong gears" so that you can see the resulting loss of performance.

Oversampled sigma-delta D/A converters and fixed-point sample rate converters can add significant amounts of distortion when playing CD-format recordings. This distortion is caused by intersample musical peaks that overload our digital playback systems. These overloads often occur many times per second, even in a well-recorded track.

This distortion can reach high amplitudes, and it can easily be measured, but it is completely invisible to traditional audio measurements. This distortion can easily be eliminated from our playback hardware, but most of the audio industry has failed to recognize this issue.

Intersample clipping may be the single most audible defect in fixed-point PCM playback systems. It is the elephant in the room.

We need to change the way we build and test our digital playback systems.  Discover The Solution...

Learn About...

• Inter-Sample Clipping
• Interpolator Overload Distortion
• Learn How These Can Be Fixed In Hardware

An Impossible Engineering Task?

Our goal was to produce an analog volume control with the highest achievable transparency. We wanted to be able to place this 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. Given the extraordinary performance of these THX-AAA amplifiers, this would not be an easy task!

Our unique solution is a fully-balanced, low-impedance, relay-controlled attenuator with over 256 steps. Nothing like this was ever built, and nothing else matches the performance of the Benchmark analog volume control system used in the LA4 and HPA4 products.

The LA4 is not Just a "Good Preamp"

The LA4 was an all-out effort to build the best line-level preamplifier on the planet.

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

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.

The AHB2 - A Radical Approach to Audio Power Amplification

Benchmark's AHB2 Power Amplifier is radically different from every other audio power amplifier on the market. It delivers the lowest distortion and lowest noise of any commercially available power amplifier. The THD+N and SNR specifications are 20 dB better than many high-end hi-fi power amplifiers. The unique high-efficiency design delivers hundreds of watts from a relatively small, passively cooled chassis.

Benchmark's lead Engineer, John Siau, will take us on a deep dive into the AHB2. You may be shocked by what is inside!

An Introduction to Benchmark

John Siau, VP and Director of Engineering, gives us an overview of his company, their design philosophy, and the pioneering products Benchmark offers for high-performance audio.

Benchmark Media, founded in 1983, has a rich history of innovation in the audio industry. Initially specializing in broadcast equipment, the company transitioned to high-end audio products in the early 2000s. Their commitment to engineering excellence has resulted in numerous accolades and a reputation for creating some of the most accurate and reliable audio equipment available.

John discusses some of Benchmark's key products, including the AHB2 power amplifier, LA4 preamp, DAC3, HPA4 headphone amp, and Studio&Stage(TM) audio cables. These products exemplify Benchmark's dedication to pushing the boundaries of audio performance, making them a favorite among audiophiles and professionals alike.