AHB2 Crossover Distortion Measurements

by John Siau March 10, 2016 3 min read

Crossover Distortion - Measurements

The following measurements and scope photos demonstrate the effectiveness of the feedforward system in the AHB2.

From the first Watt to the last Watt, the AHB2 shows no evidence of crossover distortion. In contrast, all conventional class-AB amplifiers have crossover-distortion artifacts.

Dick Olsher once said that "the first Watt is the most important Watt". I agree!

 - John Siau

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Amplifier Crossover Distortion

by John Siau March 10, 2016 7 min read

Crossover Distortion - Introduction 

Most audio power amplifiers suffer from a defect known as "crossover distortion". This distortion is particularly troublesome at low output levels. At low power levels, the crossover distortion can rise to a high percentage of the output level and become the dominant source of distortion.

- John Siau

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How Should I Buy an Audio System?

by John Siau February 26, 2016 6 min read

Two Distinct Types of Audio Products - Understand the Difference Before You Buy!

2013 Porsche 911 Carrera 4S (991) (9626546987)

Make your own choice!

"Buying an audio product is much like buying a car"

There are two distinct types of audio products. Some audio products are designed to be transparent while others are designed to provide a euphonic experience. These types are as different as a Porsche and a Cadillac.

There is not a right and wrong type of car. Likewise there is not a right and wrong type of audio product. The choice belongs to the user, but the user must be fully aware of the differences before they buy.

- John Siau

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Star Quad Cable Demonstration - Video

by John Siau February 12, 2016 1 min read

Benchmark has recorded a lab demonstration that shows what happens when a standard two-wire cable is exposed to common sources of magnetic interference.

You will be able to hear the interference, see it on an oscilloscope, and view its spectrum on an FFT. A star-quad cable is exposed to the same sources of magnetic interference and the results are compared. This demonstration shows the dramatic difference between the two cables. The star-quad cable provided a 20 to 50 dB reduction in magnetic interference, keeping the interference below audible levels.

- John Siau

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The Importance of Star-Quad Microphone Cable

by John Siau February 12, 2016 7 min read

Eliminate Magnetic Interference with Star-QuadCable

Studios, live sound venues and homes all have magnetic fields that can cause interference. Magnetic fields are produced whenever current flows through a wire. AC power cables, transformers, power supplies, computers, portable chargers, motors and light dimmers are among the devices that can emit strong magnetic fields. A microphone cable can pick up magnetic interference if it happens to pass near one of these devices. Cables can also pick up magnetic fields when they run adjacent to AC power. Star-quad cables typically reduce this magnetic interference by at least 20 to 30 dB. This is almost always enough to reduce the interference to inaudible levels.

- John Siau

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Benchmark DAC2 vs. DAC1 - Side-by-Side Measurements

by John Siau August 13, 2015 15 min read

There was a 10-year time span between the introduction of the Benchmark DAC1 and DAC2 audio D/A converters. The DAC1 defined the state of the art when it was introduced in 2002. Thirteen years later, Enjoy the Music.com selected the DAC1 as one of the 20 most significant digital audio products from the past 20 years. Today the DAC2 defines the state of the art in audio D/A conversion. John Atkinson said that the "DAC2 offered one of the highest resolutions I have measured". Both products set performance benchmarks when they were introduced. In a sense, they provide snapshots of technological progress.

This paper shows high-precision side-by-side measurements of the DAC1 and DAC2 converters. These measurements show how technology has improved, and they show that there may be two or three audible differences between these two products.

Travel through 10 years of audio technology, learn the significance of audio measurements, and see what has improved in our quest for transparent audio reproduction.

- John Siau

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Benchmark DAC2 vs. DAC1 - Is There an Audible Difference?

by John Siau August 06, 2015 9 min read

Benchmark introduced the DAC1 in 2002 and it quickly became the best-selling 2-channel professional D/A converter. To this day, the DAC1 is a standard fixture in many recording studios, and it is also a central component in many high-end hi-fi systems. In August of 2015, Enjoy the Music.com selected the DAC1 as one of the20 most significant digital audio products from the past 20 years.

It is easy to show that the DAC2 measures better than the DAC1 in almost every way. From a marketing perspective it would be tempting to claim that all of these measured differences make audible improvements, but this just isn't the case.

One reviewer, Gary Galo, recently had the opportunity to hear a DAC1 and DAC2 side-by-side. He noted some audible differences and we agree with his conclusions. We have had a great deal of experience listening to these converters side-by-side in our own listening room and we are familiar with some subtle differences.

This paper examines the subtle audible differences between the DAC1 and the DAC2. It also includes measurements that may help to explain these differences.

- John Siau

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The HPA2™ Headphone Power Amplifier

by John Siau July 22, 2015 6 min read

Why do I need a Power Amplifier to Drive My Headphones?

Many Benchmark products include our HPA2™ headphone power amplifier. Unlike most headphone amplifiers, the HPA2™ is designed to behave like a small but very clean power amplifier. What makes the HPA2™ different, and what do we mean when we say that the HPA2™ is a "power amplifier"?

- John Siau

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Box-to-Box Phase Accuracy of Benchmark DAC1 and DAC2 Converters

by John Siau October 03, 2014 3 min read

Phase Accurate Multi-Channel D/A Conversion

- Using Multiple DAC1 or DAC2 Converters

Two or more Benchmark DAC1 or DAC2 converters can be used together in phase-coherent multichannel audio systems even though their internal clocks are not synchronized. This seems to defy logic, but an examination of the system details reveals why this is possible.

- John Siau

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The AHB2 - A Radical Approach to Audio Power Amplification

by John Siau July 30, 2014 6 min read


The performance of the AHB2 would not have been achievable without taking a radical approach to power amplification. In many ways, the AHB2 is a complete 180 degree departure from traditional high-end amplifier designs. There is nothing ordinary about the Benchmark AHB2!

Take a look inside this unique audio power amplifier! 

- John Siau

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The CE Mark - A Photo-Tour of Immunity Testing

by John Siau June 25, 2014 3 min read

Testing for Immunity to Interference

Most people have seen the CE mark on electronic equipment, but few have had the opportunity to witness the tests that are required to conform to the CE specifications. This post takes the reader on a behind-the-scenes photo-tour of the CE tests of Benchmark's new AHB2 power amplifier.

- John Siau

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The CE Mark - What Does it Mean, and Why Should I Care?

by John Siau June 17, 2014 4 min read

Why is the CE Mark Important?

Many electronic products have a "CE" mark affixed to the product. This mark is mandatory in European markets, but is not required on products sold elsewhere. Few people understand what this mark means and why it is important. It is often a good idea to look for this mark when purchasing a product. It is also important to understand the differences between professional and consumer audio products (as defined in the CE standards).

- John Siau

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Headphone Amplifiers - Part 2

by John Siau March 20, 2014 3 min read

It's all about control! - Headphone Output Impedance

The movement of headphone transducers must be well controlled in order to produce high-quality audio. It is easy to build a headphone amplifier that produces sound. It is an entirely different matter to produce an amplifier that is clear, clean, and enjoyable.  

Headphone amplifiers need power and accuracy to achieve control. They also need to be protected from short circuits and overload conditions. The cheap, dirty, and common way to protect the amplifier is to add a series resistor between the amplifier and the headphone jack. This simple solution protects the amplifier from short circuits and overloads. Unfortunately, the resistor isolates the headphones from the amplifier, causing a loss of control. This ...

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Headphone Amplifiers - Part 1

by John Siau March 14, 2014 3 min read

Headphones do not Behave Like a Resistor - Beware of Misleading Specifications!

A couple years ago, some of us at Benchmark noticed a weird discrepancy between our HPA2  headphone amp (built into our DAC1 and DAC2) and some comparably-priced headphone amps. The advertised specifications of all the amps were basically the same, but they sounded noticeably different. Benchmark launched a detailed investigation to identify the differences. The results were surprising and are detailed in a white paper...
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An Examination of Headphone Amplifier Performance Specifications

by John Siau November 11, 2011 1 min read

Headphone Amplifier Whitepaper

Recording Engineers and Audiophiles often distrust audio measurements and specifications. It is not uncommon to hear claims that a product measures poorly but sounds good. Occasionally we also hear claims that a product measures well but sounds bad.

This whitepaper documents significant differences between three headphone amplifiers that have nearly identical published specifications.

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Asynchronous Upsampling to 110 kHz

by John Siau July 01, 2010 4 min read

The Advantages of Asynchronous Upsampling D/A Converters

Benchmark DAC1 converters use upsampling techniques to improve the quality of the digital to analog conversion. Benchmark’s choice of 110 kHz is slightly unorthodox. It may seem more logical to upsample by 2X or 4X and convert at standard sample rates such as 88.2 kHz, 96 kHz, 176.4 kHz or even 192 kHz. Intuition may suggest that integer ratios would produce the best results. Intuition may also suggest that higher is better, and therefore 192 kHz would be the “best” choice for an output sample rate. Unfortunately, intuition often leads us down the wrong path if it is not balanced with reason and scientific analysis. Benchmark’s analysis and testing has shown that 110 kHz offers advantages over the choices that seem more reasonable.

This paper is a short summary of the decisions that led to our choice of the 110 kHz sampling rate.

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Volume Control Technologies

by Benchmark Media Systems April 24, 2010 10 min read

Fix the Weakest Link in the Audio Chain!

A playback system's volume control is often one of the weakest links in the audio chain. This is especially true when remote control is required.

Benchmark’s HDR-VC™ (High Dynamic Range Volume Control), combines the best features of two distinct volume control methods while adding remote volume control.

  • How does a volume control degrade the sound?
  • What are the different volume control methods?
  • Are some sonically superior, and why?
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Jitter and its Effects

by John Siau February 07, 2002 5 min read

By John Siau and Allen H. Burdick


This paper addresses these questions:

  • How and where do I measure jitter, and how do I eliminate it?
  • How does sample clock jitter relate to interface jitter measured at digital output connectors?
  • How can we accurately measure jitter?
  • Why does sample clock jitter have to be so low?
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The "0-Ohm" Headphone Amplifier

by John Siau December 01, 2001 1 min read

An Introduction to "The 0-Ohm Headphone Amplifier" White Paper

The circuits used to drive headphones are often added to a product without careful consideration of the difficult loads presented by high-quality headphones. The most common circuit is an opamp driver followed by a 30-Ohm series resistor. The series resistor provides short-circuit and overload protection while isolating the opamp from the inductance and capacitance of the headphones. The series resistor protects the opamp while keeping it stable. In contrast, today's state-of-the-art headphone amplifiers eliminate the series resistor, and use a high current driver. This change reduces distortion and flattens the frequency response when a headphone is driven. These new high-end designs are often called "0-Ohm" headphone amplifiers, and are ...

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Measuring Mic-Preamp Noise

by Benchmark Media Systems January 01, 2000 2 min read

By Allen H. Burdick

To perform valid noise level measurements, two specific conditions must be established:

  1. A 150 Ohm source impedance
  2. A 20 kHz measurement bandwidth

    The microphone preamplifier must have the proper source impedance at its input. If it does not, the preamp will amplify the noise of its internal bias resistors, resulting in much higher noise voltage. Typically, the easiest way...

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